Methods for inducing cardiomyocyte proliferation

ABSTRACT

Methods for inducing cardiomyocyte proliferation, e.g., in vivo, by administering a composition comprising miRNA17-92 cluster oligonucleotides, e.g., miR-19a oligonucleotides, miR-19b oligonucleotides, or both miR-19a and miR-19b oligonucleotides.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.13/828,208, filed on Mar. 14, 2013, which claims the benefit of U.S.Provisional Patent Application No. 61/762,240, filed on Feb. 7, 2013.The entire contents of the foregoing are incorporated by referenceherein.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under Grant No. HL085635awarded by the National Institutes of Health. The Government has certainrights in the invention.

TECHNICAL FIELD

This invention relates to methods for inducing cardiomyocyteproliferation, e.g., in vivo, by administering a composition comprisinga microRNA (miRNA)-17-92 cluster miRNA, e.g., miR-17, miR-18a, miR-19a,miR-20a, miR-19b-1, and miR-92a-1, preferably miR-19a and/or miR-19b, orboth.

BACKGROUND

Cardiomyocytes in adult mammalian hearts are terminally differentiatedcells that have exited from the cell cycle and lost most of theirproliferative capacity. Death of mature cardiomyocytes in pathologicalcardiac conditions and the lack of regenerative capacity of adult heartsare primary causes of heart failure and mortality.

SUMMARY

At least in part, the present invention is based on the discovery thatmembers of miR-17-92 cluster, and miR-19a/b in particular, are requiredfor and sufficient to induce cardiomyocyte proliferation in vitro and invivo. PTEN, a tumor suppressor, was identified as a miR-17-92 target tomediate the function of miR-17-92 in cardiomyocyte proliferation. Thepresent studies therefore identify miR-17-92 as a critical regulator ofcardiomyocyte proliferation and support the use of this cluster ofmiRNAs as therapeutic targets for cardiac repair and heart regeneration.

Thus, in a first aspect, the invention provides methods for treating, orreducing the risk of developing, a myocardial infarction or chronicheart failure in a subject. The methods include identifying a subject inneed of treatment for a myocardial infarction or chronic heart failure;and administering to the subject a therapeutically effective amount ofan microRNA (miR)-microRNA (miRNA)-17-92 cluster miRNA oligonucleotide,e.g., a miR-17, miR-18a, miR-19a, miR-20a, miR-19b-1, and miR-92-1oligonucleotide, preferably a miR-19a and/or miR-19b oligonucleotide(s).

In some embodiments, the subject is over the age of 65; does not yethave chronic heart failure; or has not yet had a myocardial infarction.

In some embodiments, the therapeutically effective amount is an amountsufficient to induce cardiomyocyte proliferation.

In some embodiments, the amount of cardiomyocyte proliferation issufficient to improve cardiac function, increase cardiac contractileforce, or increase the thickness of the myocardium; and wherein themethod optionally includes detecting an improvement in cardiac function,an increase in cardiac contractile force, or an increase in thethickness of the myocardium.

In some embodiments, the oligonucleotide is a single stranded DNA or RNAthat is at least 18, 19, or 20 nucleotides long, but less than 24, 25,26, 27, 28, 29, or 30 nucleotides long, and is at least 80% identical toSEQ ID NOs: 1, 3, 6, 8, 10 or 12, preferably SEQ ID NOs: 1 or 3, with100% identity to nucleotides 1-8 of SEQ ID NOs: 1, 3, 6, 8, 10 or 12,preferably SEQ ID NOs:1 or 3, i.e., comprises the seed sequence as shownherein, plus 0 or 1 nucleotide on the 5′ end, and/or 0, 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, or 14 nucleotides on the 3′ end (up to thefull length mature sequence).

In some embodiments, the oligonucleotide comprises at least onemodification selected from the group consisting of: 5′-phosphorylation;at least one 2′-fluoro ribose modification; and a cholesterol moiety.

In some embodiments, the oligonucleotide comprises SEQ ID NOs:1, 3, 6,8, 10 or 12, preferably SEQ ID NOs:1 or 3.

In some embodiments, the oligonucleotide is a double stranded DNA orRNA, comprising: a first strand comprising a sequence that is at least80% identical to 18, 19, or 20 consecutive nucleotides of SEQ ID NOs: 1,3, 6, 8, 10 or 12, with 100% identity to nucleotides 1-8 of SEQ ID NOs:1, 3, 6, 8, 10 or 12; a second strand comprising a sequence that iscomplementary to the first strand; and an optional linker therebetween.

In some embodiments, the double stranded DNA or RNA comprises SEQ IDNO:2, 4, 5, 7, 9, 11, 13, or 14, preferably SEQ ID NOs:2 or 4.

In some embodiments, the double stranded DNA or RNA comprises at leastone modification selected from the group consisting of:5′-phosphorylation; and 2′-O-methyl ribosyl substitution at position 2in the first strand, i.e., position 2 in the sequence corresponding tothe mature miRNA.

In some embodiments, the oligonucleotide is administered locally to theheart of the subject.

In some embodiments, the oligonucleotide is administered using a virus,e.g., AAV, e.g., AAV9; a nanoparticle or microparticle delivery; or agelfoam.

In some embodiments, the subject is a post-neonatal, adolescent, oradult mammal, e.g., human. As used herein, post-neonatal refers to asubject who is beyond the newborn stage, e.g., in humans at least 3, 4,5, 6, 7, 8, 9, 10, 11 or 12 months old.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Methods and materials aredescribed herein for use in the present invention; other, suitablemethods and materials known in the art can also be used. The materials,methods, and examples are illustrative only and not intended to belimiting. All publications, patent applications, patents, sequences,database entries, and other references mentioned herein are incorporatedby reference in their entirety. In case of conflict, the presentspecification, including definitions, will control.

Other features and advantages of the invention will be apparent from thefollowing detailed description and figures, and from the claims.

DESCRIPTION OF DRAWINGS

FIGS. 1a-n . miR-17-92 is required for cardiomyocyte proliferation inembryonic, postnatal and adult hearts

-   (a) Haematoxylin and Eosin (H&E) staining of sagittal sections of    hearts from 2 days old wild type, heterozygote and mutant    miR-17-92-KO mice. Bar=1 mm.-   (b) Immunohistochemistry of phosphorylated histone H3 (phospho-H3)    on sagittal sections of hearts from 2 days old wild type,    heterozygote and mutant miR-17-92-KO mice. Bar=100 μm.-   (c) Immunohistochemistry of sagittal sections of hearts from 2 days    old wild type, heterozygote and mutant miR-17-92-KO mice. White    boxes are enlarged in lower panels. Phosphorylated histone H3 (pH3)    labels proliferating cells; α-actinin (ACTN1) marks cardiomyocytes;    DAPI labels nuclei. Bars=50 μm in upper panel and 20 μm in lower    panel.-   (d) Quantification of pH3 positive cardiomyocytes in wild type,    heterozygote and mutant miR-17-92-KO hearts from 2 days old mice.    **P<0.01 between genetic groups. (N=4˜5 each group).-   (e) Haematoxylin and Eosin (H&E) staining of transverse sections of    hearts from 10 months old wild type, heterozygote and mutant    miR-17-92-KO mice. Bar=1 mm.-   (f) Heart weight (HW) to body weight (BW) ratios of 1 year old wild    type, heterozygote and mutant miR-17-92-KO mice. N of each genotype    group listed.-   (g) Morphology of freshly isolated adult cardiomyocytes from hearts    of miR-17-92-KO and control mice. α-actinin (ACTN1) marks rod shaped    cardiomyocytes (lower panel). Bars=250 μm.-   (h) Quantification of total isolated adult cardiomyocytes from    hearts of miR-17-92-KO and control mice. N of each genotype group is    listed.-   (i) Quantitative measurement of the size of freshly isolated adult    cardiomyocytes from hearts of miR-17-92-KO and control mice. One    hundred individual cells from three different hearts were analyzed    per group. **P<0.01 between genetic groups.-   (j) Strategy of cardiac-specific knockout of mirR-17-92 cluster in    vivo.-   (k) Genotyping results of weaning age mice from intercrossing of    mir-17-92^(flox/flox) and miR-17-92^(flox/+); Nkx2-5^(Cre/+) mice.-   (l) The expression of members of the miR-17-92 cluster in 3-week old    heart samples of mir-17-92^(flox/flox), miR-17-92^(flox/+);    Nkx2-5^(Cre/+) mice, and miR-17-92^(flox/flox); Nkx2-5^(Cre/+) mice    was determined by quantitative RT-PCR. N of each genotype was    indicated.-   (m) Cross section area of cardiomyocyte in adult hearts of    mir-17-92^(flox/flox) and miR-17-92^(flox/flox); Nkx2-5^(Cre/+) mice    was measured. More than 2000 cardiomyocytes were measured from 4    hearts of each genotype.-   (n) Reduced cardiac function in cardiac-specific miR-17-92 mutant    mice. Echocardiography of cardiac function of 6-month-old    miR-17-92^(flox/flox); Nkx2-5^(Cre/+) (cKO) mice and their control    littermates. N of each genotype was indicated. *: P<0.05; **:    P<0.01. FS: Fractional shortening; LVID; d: Left ventricular end    diastolic internal dimension; LVID; s: Left ventricular end systolic    internal dimension; LVPW; d: Left ventricular end diastolic    posterior wall dimension; LVPW; s: Left ventricular end systolic    posterior wall dimension; LV Vol; d: Left ventricular end diastolic    volume.

FIGS. 2a-h . miR-17-92 induces cardiomyocyte proliferation in embryonicand postnatal hearts

-   (a) Gross morphology of hearts of 3 weeks old control and    miR-17-92-TG^(nkx2.5) mice (upper panel, bar=1 mm). Haematoxylin and    Eosin (H&E) staining of sagittal sections of 3 week old control and    miR-17-92-TG^(nkx2.5) mice (middle panel, bar=1 mm); higher    magnification of ventricle myocardium (lower panel, bar=250 μm).-   (b) Immunohistochemistry of phosphorylated histone H3 (phospho-H3)    on sagittal sections of embryonic 16.5 (E16.5) control and    miR-17-92-TG^(nkx2.5) hearts (upper panel, bar=500 μm);    Immunohistochemistry of pH3 on sagittal sections of E16.5 wild type    and miR-17-92-TG^(nkx2.5) hearts, α-actinin (ACTN1) marks    cardiomyocytes; DAPI labels nuclei (middle panel, bar=50 μm); white    boxes are enlarged in lower panels (lower panel, bar=20 μm).-   (c) Immunohistochemistry of phospho-H3 on sagittal sections of    postnatal day 4 (P4) control and miR-17-92-TG^(nkx2.5) hearts (upper    panel, bar=500 μm); Immunohistochemistry of pH3 on sagittal sections    of P4 control and miR-17-92-TG^(nkx2.5) hearts, α-actinin (ACTN1)    marks cardiomyocytes; DAPI labels nuclei (middle panel, bar=50 μm);    white boxes are enlarged in lower panels (lower panel, bar=20 μm).-   (d) Quantification of percentages of phosphorylated histone H3    (pH3⁺) cardiomyocytes in E16.5 and P4 control and    miR-17-92-TG^(nkx2.5) hearts. N=3 for each group.-   (e) The Heart Weight/Body Weight (HW/BW) ratio of 3-week-old    miR-17-92 transgenic mice (miR-17-92^(TG/TG); Nkx2-5^(Cre/+)) and    their control littermates were shown. N of each genotype was    indicated. *: P<0.05; **: P<0.01.-   (f) Strategy of cardiac-specific overexpression of miR-17-92 cluster    in vivo.-   (g) Genotyping results of weaning age mice from intercrossing of    miR-17-92^(TG/TG) and miR-17-92^(TG/+); Nkx2-5^(Cre/+) mice.-   (h) Increased expression of members of the miR-17-92 cluster in the    hearts of miR-17-92 transgenic mice. The expression of members in    miR-17-92 cluster in heart samples of miR-17-92^(TG/TG),    miR-17-92^(TG/+); αMHC-Cre and miR-17-92^(TG/TG); αMHC-Cre mice was    determined by quantitative RT-PCR. N of each genotype was indicated.

FIGS. 3a-k . miR-17-92 induces cardiomyocyte proliferation in postnataland adult hearts

-   (a) Gross morphology of hearts of 2 months old control and    miR-17-92-TG^(MHC) mice (upper panel). Haematoxylin and Eosin (H&E)    staining of transverse sections of 2 months old control and    miR-17-92-TG^(MHC) hearts (lower panels). Bars=1 mm.-   (b) Heart weight (HW) to body weight (BW) ratios of 1-, 2-, and    4-months old wild type, heterozygote and homozygote    miR-17-92-TG^(MHC) mice. N=5 for each group.-   (c) Morphology of freshly isolated adult cardiomyocytes from hearts    of miR-17-92-TG^(MHC) and control mice. α-actinin (ACTN1) marks rod    shaped cardiomyocytes (lower panel). Bars=250 μm.-   (d) Quantification of total isolated adult cardiomyocytes from 2    months old hearts of miR-17-92-TG^(MHC) and control mice. N=3 for    each genetic group.-   (e) Distribution of isolated adult cardiomyocytes with one (1),    two (2) or three (3) and more nuclei from 2 months old hearts of    miR-17-92-TG^(MHC) and control mice.-   (f) Immunohistochemistry of phosphorylated histone H3 (pH3) on    transverse sections of 15 days old control and miR-17-92-TG^(MHC)    hearts. Actinin (ACTN1) marks cardiomyocytes and DAPI labels nuclei.    Wheat germ agglutinin (WGA) staining marks cell surface (white).    White boxes are enlarged in insets.-   (g) Quantification of percentages of phosphorylated histone H3    (pH3⁺) cardiomyocytes of 15 days old control and miR-17-92-TG^(MHC)    hearts. N=4 for each genetic group.-   (h) Immunohistochemistry of EdU incorporation on transverse sections    of 15 days old control and miR-17-92-TG^(MHC) hearts. α-actinin    (ACTN1) marks cardiomyocytes and DAPI labels nuclei. Wheat germ    agglutinin (WGA) staining marks cell surface (white).-   (i) Quantification of percentages of EdU positive cardiomyocytes of    15 days old control and miR-17-92-TG^(MHC) hearts. N=3 for each    genetic group.-   (j) Cardiac-specific overexpression of miR-17-92 does not change the    size of cardiomyocyte. Transverse sections from hearts of    2-month-old miR-17-92^(TG/TG) and miR-17-92^(TG/TG); αMHC-Cre mice    were stained with Wheat Germ Agglutanin (WGA) to show the cross    section area of cardiomyocyte. Measurement of the cross section area    of cardiomyocyte show no significant (ns) difference between two    genotypes.-   (k) Similar staining and measurement as in 3(j) were also performed    on 4-month old heart samples and no significant difference was found    between the two genotypes. More than 2000 cardiomyocytes were    measured from at least 3 hearts of each genotype. Bar=100 μm.

FIGS. 4a-i . Control of cardiomyocyte proliferation by miR-17-92 inadult heart in response to myocardial infarction

-   (a) Gross morphology of hearts of 6 months old    miR-17-92-TG^(MerCreMer) and control mice after tamoxifen    administration (upper panels). Haematoxylin and Eosin (H&E) staining    of transverse sections of control and miR-17-92-TG^(MerCreMer)    hearts (lower panels). Bars=1 mm.-   (b) Immunohistochemistry of EdU incorporation on sagittal sections    of 6 months old miR-17-92-TG^(MerCreMer) and control mice after    tamoxifen administration (upper panels, bar=500 μm);    Immunohistochemistry of EdU on sagittal sections of 6 months old    miR-17-92-TG^(MerCreMer) and control mice after tamoxifen    administration. The arrow points to EdU positive signal in    cardiomyocytes. α-actinin (ACTN1) marks cardiomyocytes; DAPI labels    nuclei (lower panels, bar=20 μm).-   (c) Quantification of total isolated adult cardiomyocytes from    hearts of 6 months old miR-17-92-TG^(MerCreMer) and control mice    after tamoxifen administration. N=3 for each group.-   (d) Quantitative measurement of the size of freshly isolated adult    cardiomyocytes from hearts of miR-17-92-TG^(MerCreMer) and control    mice. One hundred individual cells from three different hearts were    analyzed per group. **P<0.01 between genetic groups.-   (e) Scheme of experimental procedure to introduce myocardial    infarction (MI), tamoxifin and EdU injection and echocardiography    measurement.-   (f) Representative images of series of transverse sections of 6    months old miR-17-92-TG^(MerCreMer) and control mice after MI and    tamoxifen administration. Sirius red/fast green collagen staining    marks myocardium (green) and scar (red). Bars=1 mm.-   (g) Quantification of the size of scar in the hearts of    miR-17-92-TG^(MerCreMer) (N=4) and control mice (N=5) after MI and    tamoxifen administration. *P<0.05 between genetic groups.-   (h) Immunohistochemistry of EdU on sagittal sections of 6 months old    miR-17-92-TG^(MerCreMer) and control mice after tamoxifen    administration. White boxes are enlarged in insets and arrows point    to EdU positive signal. α-actinin (ACTN1) marks cardiomyocytes; DAPI    labels nuclei. Bars=50 μm).-   (i) Induced overexpression of miR-17-92 in the heart. The expression    of members of miR-17-92 cluster in 5-month-old heart samples after    tamoxifen administration (4 months after tamoxifen administration)    in miR-17-92^(TG/TG) and miR-17-92^(TG/TG); αMHC-MerCreMer    (MerCreMer) mice was determined by quantitative RT-PCR. N of each    genotype was indicated.

FIGS. 5a-i . miR-17-92 regulates cardiomyocyte proliferation andrepresses the expression and function of PTEN

-   (a) Quantification of percentages of EdU⁺ cardiomyocytes in cultured    neonatal rat cardiomyocytes after treatment with miRNA mimics or    control.-   (b) Quantification of percentages of EdU⁺ cardiomyocytes in cultured    neonatal rat cardiomyocytes after treatment with miRNA inhibitors or    control.-   (c) Quantification RT-PCR (qPCR) analyses of CDK1 expression in    cultured neonatal rat cardiomyocytes after treatment with miRNA    mimics or mimic control.-   (d) Quantification of percentages of EdU⁺ cardiomyocytes in cultured    neonatal mouse cardiomyocytes isolated from miR-17-92^(TG/TG) mice    and transduced with Ad-cTNT-Cre or Ad-lacZ in control. **P<0.01.-   (e) Quantification RT-PCR (qPCR) analyses of the expression of    putative miR-17-92 targets the hearts of 20 days old miR-17-92-KO    and control mice.-   (f) Quantification RT-PCR (qPCR) analyses of the expression of    putative miR-17-92 targets the hearts of 15 days old    miR-17-92-TG^(MHC) and control mice.-   (g) Quantification of percentages of EdU⁺ cardiomyocytes in cultured    neonatal rat cardiomyocytes after treatment with miR-19a/b mimics,    control mimics, modify RNA for PTEN (modi-PTEN), or both miR-19a/b    mimics and modi-PTEN.-   (h) Overexpression of miR-17-92 induces the proliferation of P4    neonatal rat cardiomyocyte. (a) Proliferating neonatal rat    cardiomyocytes were determined by detecting the EDU positive    cardiomyocyte with immunochemistry. The boxed areas in upper panels    are enlarged in lower panels. Bar=60 μm in upper panels; Bar=15 μm    in lower panels. (b) Quantification of the percentage of EDU    positive cardiomyocyte in each experimental group.-   (i) A Western blot showing the overexpression of FLAG-tagged PTEN    protein in modified RNA transfected neonatal rat cardiomyocytes.

FIGS. 6a-c . Hairpin sequences of miR19a/b

-   (a) Hairpin sequences of human miR19-a (SEQ ID NO: 2).-   (b) Hairpin sequences of human miR19-b-1 (SEQ ID NO: 4).-   (c) Hairpin sequences of human miR19-b-2 (SEQ ID NO: 5).

FIG. 7A. Increased expression of miR-19a after intra-cardiac injectionof miR-19a/19b mimics in post-myocardial infarction (MI) hearts. Bargraph showing miR-19a expression level determined by real-time Q-PCRusing whole heart tissue 3-days after the surgery and mimic injection. Nof each group is indicated. **: P<0.01 vs control group.

FIG. 7B. Improved cardiac function after miR-19a/19b administration postmyocardium infarction (MI). Bar graphs showing the results ofechocardiography analyses of cardiac function were performed at 2 and 4weeks post-MI surgery from miR-19a/19b and control groups. N of eachgroup is indicated. *: P<0.05; **: P<0.01 vs control group. LVPW; d:Left ventricular end diastolic posterior wall dimension (left graph);FS: Fractional shortening (right graph).

FIG. 7C. Reduced infarct size after intra-cardiac injection ofmiR-19a/19b miR-19a/19b mimics in post-myocardial infarction (MI)hearts. Representative images of series of transverse sections of hearts4 weeks after miR-19a/19b or control injection. Sirius red/fast greencollagen staining marks myocardium (green) and scar (red).

DETAILED DESCRIPTION

The adult mammalian heart has limited capability to regenerate itselfafter the loss of mature cardiomyocytes due to a variety of pathologicalconditions such as myocardial infarction. It is generally accepted thatpost-mitotic cardiomyocytes in adult Mammalian hearts exit from the cellcycle and stop cell proliferation^(1,2). However, the hearts of adultzebrafish can undergo cardiac regeneration without scar formation afterresection of ventricle, primarily through cardiomyocyteproliferation³⁻⁶. Intriguingly, a recent report demonstrated thatsurgical resection of the ventricular apex in newborn mice stimulatesthe proliferation of cardiomyocytes and repairs the damaged heart, butthe mouse heart loses this regenerative potential within 7 days of itspostnatal life and it is not clear how the regenerative potential islost in the adult hearts⁷. To date, the molecular mechanism andregulatory pathways that control adult cardiomyocyte proliferation andcardiac regeneration remain largely unknown.

miRNAs are a class of ˜22 nt non-coding RNAs that regulate theexpression of protein-coding genes post-transcriptionally. Genesencoding miRNAs are transcribed as long primary transcripts (pri-miRNAs)that contain a stem-loop hairpin structure (Lee et al., EMBO J.21:4663-70, 2002). Pri-miRNAs are sequentially processed by the RNaseIIIenzymes Drosha and Dicer to yield mature miRNA duplexes of 18 to 24nucleotides in length (Lee et al., Nature 425:415-9, 2003; Hutvagner andZamore, Science, 297:2056-60, 2002).

More than 1,000 human miRNAs have been identified; however, thebiological functions of many of them remain unknown. The miR-17-92cluster, a polycistronic miRNA cluster that contains multiple miRNAcomponents (the precursor transcript derived from the mir-17-92 genecontains six tandem stem-loop hairpin structures that yield six maturemiRNAs: miR-17, miR-18a, miR-19a, miR-20a, miR-19b-1, and miR-92-1), wasinitially reported as a human oncogene and named oncomir1^(8, 9).Numerous reports have documented the expression of miR-17-92 in varietyof human cancers and disorders¹⁰⁻¹². Genetic studies demonstrated thatmiR-17-92 is indispensable for mouse development and cell proliferation,and miR-17-92 mutant mice die postnatally, displaying defects in lung,hearts and others¹³⁻¹⁵.

The present inventors hypothesized that miR-17-92 might regulate theproliferation of cardiomyocytes. In the present study, the miR-17-92cluster was tissue-specifically overexpressed or deleted incardiomyocytes in transgenic or knockout mice. As demonstrated herein,miR-17-92, and specifically miR-19a/b, participates in the regulation ofcardiomyocyte proliferation in embryonic, postnatal and adult hearts.

In sharp contrast to embryonic cardiomyocytes, which exhibit strongproliferative activity, the rate of cardiomyocyte proliferation and turnover in adult hearts is very low and it is generally conceived thatadult hearts retain very limited (if any) potential for regeneration. Asa consequence, the intrinsic renewal rate is insufficient to reversecardiomyocyte loss and to restore cardiac function underpathophysiological conditions^(27, 28). Numerous attempts have beendeveloped to overcome this hurdle and one of the approaches is to inducecell cycle activity in the surviving cardiomyocytes^(27, 29). Previousreports indicate that targeted overexpression of members of the cyclinD, cyclin D2 in particularly, is sufficient to induce cardiomyocyte cellcycle activity in adult hearts, resulting in improved cardiac functionupon myocardial injury³⁰⁻³². Despite the fact that the critical role ofthe cell cycle regulators in cardiomyocyte proliferation is known, themolecular pathways that diminish adult cardiomyocyte proliferationremain largely unknown. The studies reported here demonstrated for thefirst time that miRNAs are previously unidentified regulators ofcardiomyocyte proliferation. miR-19a/miR-19b are sufficient and requiredfor neonatal cardiomyocyte proliferation in vitro, consistent with theview that miR-19 is a key component of the miR-17-92 cluster incontrolling cell proliferation in postmitotic cardiac myocytes. ThesemiRNAs can be used to reconstitute lost cardiomyocytes in injured adulthearts, and thus are of considerable therapeutic value for humancardiovascular disease.

miRNA 17-92 Cluster miRNAs

MicroRNAs (miRNAs) are a class of small (e.g., 18-24 nucleotides)non-coding RNAs that exist in a variety of organisms, including mammals,and are conserved in evolution. miRNAs are processed from hairpinprecursors of about 70 nucleotides which are derived from primarytranscripts through sequential cleavage by the RNAse III enzymes droshaand dicer. Many microRNAs can be encoded in intergenic regions, hostedwithin introns of pre-mRNAs or within ncRNA genes. Many miRNAs also tendto be clustered and transcribed as polycistrons and often have similarspatial temporal expression patterns. MiRNAs have been found to haveroles in a variety of biological processes including developmentaltiming, differentiation, apoptosis, cell proliferation, organdevelopment, and metabolism.

The present methods include the administration and use of miR-17-92cluster miRNAs, e.g., miR-17, miR-18a, miR-19a, miR-20a, miR-19b-1, andmiR-92-1; preferably miRNA 19a and/or 19b, as well as mimics thereof.Preferably human sequences are used, though other sequences are alsoknown in the art and can also be used for the present methods, e.g., innon-human animals. The mouse miRNA sequences are identical to the humansequences.

miRNA-19a

The mature sequence of human miR-19a is UGUGCAAAUCUAUGCAAAACUGA (SEQ IDNO: 1). The mature sequence is excised from the 3′ arm of the hairpinprecursor. The sequence of the miRNA19a hairpin precursor isGCAGUCCUCUGUUAGUUUUGCAUAGUUGCACUACAAGAAGAAUGUAGUUGUGCAAAUCUAUGCAAAACUGAUGGUGGCCUGC (SEQ ID NO:2), which is coded onchromosome 13. The hairpin structure of miR-19a is shown in FIG. 6 a.

miRNA-19b

The mature sequence of human miR-19b-1 is UGUGCAAAUCCAUGCAAAACUGA (SEQID NO:3). The mature sequence is excised from the 3′ arm of the hairpinprecursor. The sequence of the miRNA19b-1 hairpin precursor isCACUGUUCUAUGGUUAGUUUUGCAGGUUUGCAUCCAGCUGUGUGAUAUUCUGCUGUGCAAAUCCAUGCAAAACUGACUGUGGUAGUG (SEQ ID NO:4), which is coded onchromosome 13. The hairpin structure of miR-19b-1 is shown in FIG. 6 b.

The mature sequence of human miR-19b-2 is identical to that ofmiR-19b-1, i.e., UGUGCAAAUCCAUGCAAAACUGA (SEQ ID NO:3). The maturesequence is excised from the 3′ arm of the hairpin precursor. Thesequence of the miRNA19b-2 hairpin precursor isACAUUGCUACUUACAAUUAGUUUUGCAGGUUUGCAUUUCAGCGUAUAUAUGUAUAUGUGGCUGUGCAAAUCCAUGCAAAACUGAUUGUGAUAAUGU (SEQ ID NO:5), which iscoded on the X chromosome. The hairpin structure of miR-19a is shown inFIG. 6c . Although not part of miR-17-92, miR-19b-2 shares nearlyidentical (one mismatch) nucleic sequences as miR-19a and likely willfunctions in the same manner.

miRNA-17

The mature sequence of human miR-17 is CAAAGUGCUUACAGUGCAGGUAG (SEQ IDNO:6). The sequence of the miRNA17 hairpin precursor isGUCAGAAUAAUGUCAAAGUGCUUACAGUGCAGGUAGUGAUAUGUGCAUCUACUGCAGUGAAGGCACUUGUAGCAUUAUGGUGAC (SEQ ID NO:7).

miRNA-18a

The mature sequence of human miR-18a is UAAGGUGCAUCUAGUGCAGAUAG (SEQ IDNO:8). The sequence of the miR-18a hairpin precursor isUGUUCUAAGGUGCAUCUAGUGCAGAUAGUGAAGUAGAUUAGCAUCUACUG CCCUAAGUGCUCCUUCUGGCA(SEQ ID NO:9).

miRNA-20a

The mature sequence of human miR-20a is UAAAGUGCUUAUAGUGCAGGUAG (SEQ IDNO:10). The sequence of the miR-20a hairpin precursor isGUAGCACUAAAGUGCUUAUAGUGCAGGUAGUGUUUAGUUAUCUACUGCAU UAUGAGCACUUAAAGUACUGC(SEQ ID NO: 11).

miRNA-92a

The mature sequence of human miR-92a-1 is UAUUGCACUUGUCCCGGCCUGU (SEQ IDNO:12). The sequence of the miR-92a-1 hairpin precursor, encoded onchromosome 13, is CUUUCUACACAGGUUGGGAUCGGUUGCAAUGCUGUGUUUCUGUAUGGUAUUGCACUUGUCCCGGCCUGUUGAGUUUGG (SEQ ID NO: 13).

The mature sequence of human miR-92a-2 is identical to that ofmiR-92a-1, i.e., UAUUGCACUUGUCCCGGCCUGU (SEQ ID NO:12). The sequence ofthe miR-92a-2 hairpin precursor isUCAUCCCUGGGUGGGGAUUUGUUGCAUUACUUGUGUUCUAUAUAAAGUAUUGCACUUGUCCCGGCCUGUGGAAGA (SEQ ID NO: 14), which is coded on the Xchromosome. Although not part of miR-17-92, miR-92a-2 shares nearlyidentical (one mismatch) nucleic sequences as miR-92a-1 and likely willfunctions in the same manner.

Seed Sequence

The following table sets forth the seed sequences for the miR-17-92cluster miRNAS:

microRNA Seed sequence SEQ ID NO: miR-17 AAAGUG 15 miR-20a AAAGUG 16miR-18a AAGGUG 17 miR-19a GUGCAA 18 miR-19b GUGCAA 19 miR-92a AUUGCA 20

Methods of Treatment

As described herein, miR-17-92 cluster oligonucleotides can be used toinduce proliferation of cardiomyocytes, e.g., in vivo. Thus, theseoligonucleotides can be used to treat conditions in which cardiomyocyteproliferation would be desirable, e.g., ischemic injury, e.g., aftermyocardial infarction (MI); after injury to the heart, e.g., as a resultof cardiotoxic drugs (e.g., anthracycline antibiotics (e.g.,doxorubicin), cocaine, methamphetamine, cyclic antidepressants, calciumchannel blockers, beta-blockers, and digoxin) or trauma (whetheraccidental or intentional as a result of surgery); heart failure; ordiminished cardiac capacity associated with normal aging.

In these methods, a therapeutically effective amount of a miR-17-92cluster oligonucleotide is administered to the subject. In someembodiments, delivery of the oligonucleotide is targeted to theappropriate cell type, e.g., cardiomyocytes or cardiac tissue, toprevent unwanted side-effects.

A number of methods are known in the art for delivery of miRNA-17-92cluster oligonucleotides, e.g., using adenoassociated viruses (AAV)- orlentiviral-mediated miRNA delivery (using a method substantially asdescribed in Kota et al., Cell. 137(6): 1005-1017, 2009, or Wang et al.,“Increased expression of microRNA-146a decreases myocardialischaemia/reperfusion injury,” Cardiovasc Res. 2013. doi:10.1093/cvr/cvs356); nano-particle mediated miRNA delivery (e.g., asdescribed in Cheng and Salzman, Mol. Pharmaceutics, 9(5):1481-1488,2012); gelfoam-mediated intrapericardial miRNA delivery (Polizzotti etal., PLoS One 2012; 7:e36788); and/or direct intramuscularadministration of miRNAs in the heart (e.g., as described in Shan etal., “Upregulation of microRNA-1 and microRNA-133 contributes toarsenic-induced cardiac electrical remodeling,” Int J Cardiol. 2012.doi:10.1016/j.ijcard.2012.07.009; Kukreja et al., Mol Pharmacol. 80(4):558-564, 2011).

A preferred way to increase the level of a miRNA is by the use ofadenoassociated viruses (AAV), which allows the miRNA to be continuallyexpressed. Additionally, the use of cardiotropic AAV serotypes ormutants improves tissue specificity. Thus, for example, the methods mayinclude delivering the oligonucleotides in a cardiotropic AAV, e.g., asdescribed in Tilemann et al., Circulation Research. 2012; 110: 777-793.In some embodiments, AAV9 is used as described in Bish et al., HumanGene Therapy (2008) 19(12): 1359-1368 and Katare et al., Circ Res. 2011May 13; 108(10):1238-51.

The use of tissue-specific promoters for expression allows for furtherspecificity in addition to the AAV serotype. Furthermore, AAV iscurrently in use in a number of clinical trials for gene therapy, ofwhich the safety profiles have looked quite well. In line with this,Kota et al 5 recently showed AAV-mediated delivery of miR-26a bluntstumor genesis in a mouse model of liver cancer.

The methods can include administering oligonucleotides consisting of amature miRNA sequence (e.g., one, two, or all three of SEQ ID NOs: 1, 3,6, 8, 10 or 12, preferably SEQ ID NOs: 1 or 3), or a hairpin sequence(e.g., one, two, or all three of SEQ ID NO:2, 4, 5, 7, 9, 11, 13, or 14,preferably SEQ ID NOs:2 or 4). Alternatively, an oligonucleotide that isshorter than the full length miRNA sequence, but comprises at least theseed sequence of the miRNA, can be administered. The oligonucleotidescan thus include at least 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22 or 23 of the nucleotides of the mature miRNA, comprisingat least the seed sequence, preferably 19 nucleotides or more, and canhave up to 20% sequence variation (i.e., non-identity) so long as theoligonucleotides retain the ability to induce proliferation ofcardiomyocytes, e.g., as determined be an assay described herein, e.g.,an in vitro assay. Preferably any non-identity is outside of the seedsequence, e.g., not in the first 8 nucleotides at the 5′ end of themiRNA.

In some embodiments, where sequences longer than the seed sequence areused, the methods include administering both miR-19a and miR-19boligonucleotides.

In some embodiments, the miR-17-92 cluster oligonucleotides can beadministered as synthetic ssRNA, dsRNA, dsDNA, or in an expressionvector, e.g., a viral expression vector. In some embodiments, theoligonucleotide is a miRNA mimic, e.g., synthetic RNA duplexes designedto mimic the endogenous functions of the miRNA of interest, withmodifications for stability and cellular uptake. The “guide strand” isidentical to the miRNA of interest, whereas the “passenger strand” ismodified and typically linked to a molecule such as cholesterol forenhanced cellular uptake.

The oligonucleotides can be ssRNA, dsRNA, dsDNA, or miRNA mimics thatinclude one or more modifications, e.g., one or more of the followingmodifications. The oligonucleotide must function as a miRNA and the cellmust recognize it as such, which limits the allowed so the chemicalmodifications.

In some embodiments, the oligonucleotides comprise at least onenucleotide modified at the 2′ position of the sugar, most preferably a2′-O-alkyl, 2′-O-alkyl-O-alkyl or 2′-fluoro-modified nucleotide. Inother preferred embodiments, RNA modifications include 2′-fluoro,2′-amino and 2′ O-methyl modifications on the ribose of pyrimidines,abasic residues or an inverted base at the 3′ end of the RNA. Suchmodifications are routinely incorporated into oligonucleotides and theseoligonucleotides have been shown to have a higher Tm (i.e., highertarget binding affinity) than; 2′-deoxyoligonucleotides against a giventarget.

A number of nucleotide and nucleoside modifications have been shown tomake the oligonucleotide into which they are incorporated more resistantto nuclease digestion than the native oligodeoxynucleotide; thesemodified oligos survive intact for a longer time than unmodifiedoligonucleotides. Specific examples of modified oligonucleotides includethose comprising modified backbones, for example, phosphorothioates,phosphotriesters, methyl phosphonates, short chain alkyl or cycloalkylintersugar linkages or short chain heteroatomic or heterocyclicintersugar linkages. Most preferred are oligonucleotides withphosphorothioate backbones and those with heteroatom backbones,particularly CH2-NH—O—CH2, CH,˜N(CH3)˜O˜CH2 (known as amethylene(methylimino) or MMI backbone], CH2-O—N(CH3)-CH2,CH2-N(CH3)-N(CH3)-CH2 and O—N(CH3)-CH2-CH2 backbones, wherein the nativephosphodiester backbone is represented as O—P—O—CH,); amide backbones(see De Mesmaeker et al. Ace. Chem. Res. 1995, 28:366-374); morpholinobackbone structures (see Summerton and Weller, U.S. Pat. No. 5,034,506);peptide nucleic acid (PNA) backbone (wherein the phosphodiester backboneof the oligonucleotide is replaced with a polyamide backbone, thenucleotides being bound directly or indirectly to the aza nitrogen atomsof the polyamide backbone, see Nielsen et al., Science 1991, 254, 1497).Phosphorus-containing linkages include, but are not limited to,phosphorothioates, chiral phosphorothioates, phosphorodithioates,phosphotriesters, aminoalkylphosphotriesters, methyl and other alkylphosphonates comprising 3′alkylene phosphonates and chiral phosphonates,phosphinates, phosphoramidates comprising 3′-amino phosphoramidate andaminoalkylphosphoramidates, thionophosphoramidates,thionoalkylphosphonates, thionoalkylphosphotriesters, andboranophosphates having normal 3′-5′ linkages, 2′-5′ linked analogs ofthese, and those having inverted polarity wherein the adjacent pairs ofnucleoside units are linked 3′-5′ to 5′-3′ or 2′-5′ to 5′-2′; see U.S.Pat. Nos. 3,687,808; 4,469,863; 4,476,301; 5,023,243; 5,177,196;5,188,897; 5,264,423; 5,276,019; 5,278,302; 5,286,717; 5,321,131;5,399,676; 5,405,939; 5,453,496; 5,455, 233; 5,466,677; 5,476,925;5,519,126; 5,536,821; 5,541,306; 5,550,111; 5,563, 253; 5,571,799;5,587,361; and 5,625,050. In some embodiments, the oligonucleotidesinclude phosphorothioate at least the first, second, or thirdinternucleotide linkage at the 5′ or 3′ end of the nucleotide sequence.

Morpholino-based oligomeric compounds are described in Dwaine A. Braaschand David R. Corey, Biochemistry, 2002, 41(14), 4503-4510); Genesis,volume 30, issue 3, 2001; Heasman, J., Dev. Biol., 2002, 243, 209-214;Nasevicius et al., Nat. Genet., 2000, 26, 216-220; Lacerra et al., Proc.Natl. Acad. Sci., 2000, 97, 9591-9596; and U.S. Pat. No. 5,034,506,issued Jul. 23, 1991.

Cyclohexenyl nucleic acid oligonucleotide mimetics are described in Wanget al., J. Am. Chem. Soc., 2000, 122, 8595-8602.

Modified oligonucleotide backbones that do not include a phosphorus atomtherein have backbones that are formed by short chain alkyl orcycloalkyl internucleoside linkages, mixed heteroatom and alkyl orcycloalkyl internucleoside linkages, or one or more short chainheteroatomic or heterocyclic internucleoside linkages. These comprisethose having morpholino linkages (formed in part from the sugar portionof a nucleoside); siloxane backbones; sulfide, sulfoxide and sulfonebackbones; formacetyl and thioformacetyl backbones; methylene formacetyland thioformacetyl backbones; alkene containing backbones; sulfamatebackbones; methyleneimino and methylenehydrazino backbones; sulfonateand sulfonamide backbones; amide backbones; and others having mixed N,O, S and CH2 component parts; see U.S. Pat. Nos. 5,034,506; 5,166,315;5,185,444; 5,214,134; 5,216,141; 5,235,033; 5,264,562; 5,264,564;5,405,938; 5,434,257; 5,466,677; 5,470,967; 5,489,677; 5,541,307;5,561,225; 5,596,086; 5,602,240; 5,610,289; 5,602,240; 5,608,046;5,610,289; 5,618,704; 5,623,070; 5,663,312; 5,633,360; 5,677,437; and5,677,439, each of which is herein incorporated by reference.

One or more substituted sugar moieties can also be included, e.g., oneof the following at the 2′ position: OH, SH, SCH₃, F, OCN, OCH₃OCH₃,OCH₃O(CH₂)nCH₃, O(CH₂)nNH₂ or O(CH₂)nCH₃ where n is from 1 to about 10;C₁ to C₁₀ lower alkyl, alkoxyalkoxy, substituted lower alkyl, alkaryl oraralkyl; Cl; Br; CN; CF3; OCF3; O-, S-, or N-alkyl; O-, S-, orN-alkenyl; SOCH3; SO2 CH3; ONO2; NO2; N3; NH2; heterocycloalkyl;heterocycloalkaryl; aminoalkylamino; polyalkylamino; substituted silyl;an RNA cleaving group; a reporter group; an intercalator; a group forimproving the pharmacokinetic properties of an oligonucleotide; or agroup for improving the pharmacodynamic properties of an oligonucleotideand other substituents having similar properties. As another example,the nucleic acid sequence can include a 2′-modified nucleotide, e.g., a2′-deoxy, 2′-deoxy-2′-fluoro, 2′-O-methyl, 2′-O-methoxyethyl (2′-O-MOE),2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE),2′-O-dimethylaminopropyl (2′-O-DMAP), 2′-O-dimethylaminoethyloxyethyl(2′-O-DMAEOE), or 2′-O—N-methylacetamido (2′-O-NMA). As another example,the nucleic acid sequence can include at least one 2′-O-methyl-modifiednucleotide, and in some embodiments, all of the nucleotides include a2′-O-methyl modification. A preferred modification includes2′-methoxyethoxy [2′-0-CH₂CH₂OCH₃, also known as2′-O-(2-methoxyethyl)](Martin et al, HeIv. Chim. Acta, 1995, 78, 486).Other preferred modifications include 2′-methoxy (2′-O—CH₃), 2′-propoxy(2′-OCH₂CH₂CH₃) and 2′-fluoro (2′-F). Similar modifications may also bemade at other positions on the oligonucleotide, particularly the 3′position of the sugar on the 3′ terminal nucleotide and the 5′ positionof 5′ terminal nucleotide. Oligonucleotides may also have sugar mimeticssuch as cyclobutyls in place of the pentofuranosyl group.

In some embodiments, both a sugar and an internucleoside linkage, i.e.,the backbone, of the nucleotide units are replaced with novel groups.The base units are maintained for hybridization with an appropriatenucleic acid target compound. One such oligomeric compound, anoligonucleotide mimetic that has been shown to have excellenthybridization properties, is referred to as a peptide nucleic acid(PNA). In PNA compounds, the sugar-backbone of an oligonucleotide isreplaced with an amide containing backbone, for example, anaminoethylglycine backbone. The nucleobases are retained and are bounddirectly or indirectly to aza nitrogen atoms of the amide portion of thebackbone. Representative United States patents that teach thepreparation of PNA compounds comprise, but are not limited to, U.S. Pat.Nos. 5,539,082; 5,714,331; and 5,719,262, each of which is hereinincorporated by reference. Further teaching of PNA compounds can befound in Nielsen et al, Science, 1991, 254, 1497-1500.

Oligonucleotides can also include, additionally or alternatively,nucleobase (often referred to in the art simply as “base”) modificationsor substitutions. As used herein, “unmodified” or “natural” nucleobasesinclude adenine (A), guanine (G), thymine (T), cytosine (C) and uracil(U). Modified nucleobases include nucleobases found only infrequently ortransiently in natural nucleic acids, e.g., hypoxanthine,6-methyladenine, 5-Me pyrimidines, particularly 5-methylcytosine (alsoreferred to as 5-methyl-2′ deoxycytosine and often referred to in theart as 5-Me-C), 5-hydroxymethylcytosine (HMC), glycosyl HMC andgentobiosyl HMC, as well as synthetic nucleobases, e.g., 2-aminoadenine,2-(methylamino)adenine, 2-(imidazolylalkyl)adenine,2-(aminoalklyamino)adenine or other heterosubstituted alkyladenines,2-thiouracil, 2-thiothymine, 5-bromouracil, 5-hydroxymethyluracil,8-azaguanine, 7-deazaguanine, N6 (6-aminohexyl)adenine and2,6-diaminopurine. Kornberg, A., DNA Replication, W. H. Freeman & Co.,San Francisco, 1980, pp 75-77; Gebeyehu, G., et al. Nucl. Acids Res.1987, 15:4513). A “universal” base known in the art, e.g., inosine, canalso be included. 5-Me-C substitutions have been shown to increasenucleic acid duplex stability by 0.6-1.2<0>C. (Sanghvi, Y. S., inCrooke, S. T. and Lebleu, B., eds., Antisense Research and Applications,CRC Press, Boca Raton, 1993, pp. 276-278) and are presently preferredbase substitutions.

Modified nucleobases also comprise other synthetic and naturalnucleobases such as 5-methylcytosine (5-me-C), 5-hydroxymethyl cytosine,xanthine, hypoxanthine, 2-aminoadenine, 6-methyl and other alkylderivatives of adenine and guanine, 2-propyl and other alkyl derivativesof adenine and guanine, 2-thiouracil, 2-thiothymine and 2-thiocytosine,5-halouracil and cytosine, 5-propynyl uracil and cytosine, 6-azo uracil,cytosine and thymine, 5-uracil (pseudo-uracil), 4-thiouracil, 8-halo,8-amino, 8-thiol, 8-thioalkyl, 8-hydroxyl and other 8-substitutedadenines and guanines, 5-halo particularly 5-bromo, 5-trifluoromethyland other 5-substituted uracils and cytosines, 7-methylquanine and7-methyladenine, 8-azaguanine and 8-azaadenine, 7-deazaguanine and7-deazaadenine and 3-deazaguanine and 3-deazaadenine.

Further, nucleobases comprise those disclosed in U.S. Pat. No.3,687,808, those disclosed in ‘The Concise Encyclopedia of PolymerScience And Engineering’, pages 858-859, Kroschwitz, J. I., ed. JohnWiley & Sons, 1990, those disclosed by Englisch et al., AngewandleChemie, International Edition’, 1991, 30, page 613, and those disclosedby Sanghvi, Y. S., Chapter 15, Antisense Research and Applications’,pages 289-302, Crooke, S. T. and Lebleu, B. ea., CRC Press, 1993.Certain of these nucleobases are particularly useful for increasing thebinding affinity of the oligomeric compounds of the invention. Theseinclude 5-substituted pyrimidines, 6-azapyrimidines and N-2, N-6 and 0-6substituted purines, comprising 2-aminopropyladenine, 5-propynyluraciland 5-propynylcytosine. 5-methylcytosine substitutions have been shownto increase nucleic acid duplex stability by 0.6-1.2<0>C (Sanghvi, Y.S., Crooke, S. T. and Lebleu, B., eds, ‘Antisense Research andApplications’, CRC Press, Boca Raton, 1993, pp. 276-278) and arepresently preferred base substitutions, even more particularly whencombined with 2′-O-methoxyethyl sugar modifications. Modifiednucleobases are described in U.S. Pat. No. 3,687,808, as well as U.S.Pat. Nos. 4,845,205; 5,130,302; 5,134,066; 5,175, 273; 5, 367,066;5,432,272; 5,457,187; 5,459,255; 5,484,908; 5,502,177; 5,525,711;5,552,540; 5,587,469; 5,596,091; 5,614,617; 5,750,692, and 5,681,941,each of which is herein incorporated by reference.

In some embodiments, the oligonucleotides used in the methods describedherein comprise one or more locked nucleic acid (LNA) molecules,including [alpha]-L-LNAs. LNAs comprise ribonucleic acid analogueswherein the ribose ring is “locked” by a methylene bridge between the2′-oxgygen and the 4′-carbon—i.e., oligonucleotides containing at leastone LNA monomer, that is, one 2′-O,4′-C-methylene-β-D-ribofuranosylnucleotide. LNA bases form standard Watson-Crick base pairs but thelocked configuration increases the rate and stability of the basepairingreaction (Jepsen et al., Oligonucleotides, 14, 130-146 (2004)). LNAsalso have increased affinity to base pair with RNA as compared to DNA.Thus in some embodiments, the oligonucleotides are “locked,” i.e.,comprise nucleic acid analogues in which the ribose ring is “locked” bya methylene bridge connecting the 2′-O atom and the 4′-C atom (see,e.g., Kaupinnen et al., Drug Disc. Today 2(3):287-290 (2005); Koshkin etal., J. Am. Chem. Soc., 120(50):13252-13253 (1998)). For additionalmodifications, and discussions of modifications and methods of using thesame, see US 20100004320, US 20090298916, and US 20090143326, as well asEgli and Gryaznov, Cellular and Molecular Life Sciences 57(10):1440-1456(2000); Eulalio et al., “Functional screening identifies miRNAs inducingcardiac regeneration,” Nature (2012) doi: 10.1038/nature11739; Wang,Methods Mol Biol. 2011; 676:211-23; McManus et al., RNA. 2002 June;8(6):842-50; and Chorn et al., RNA. 18: 1796-1804 (2012). In someembodiments, the oligonucleotides are 5′-phosphorylated and contain atleast one 2′-fluoro ribose modification (Chorn et al., RNA. 18:1796-1804 (2012)). In some embodiments, the oligonucleotides include a2′-O-methyl ribosyl substitution at position 2 in the guide strand(Jackson et al., RNA. 2006 July; 12(7): 1197-1205).

The oligonucleotides can be designed using any method known in the art;a number of algorithms are known, and are commercially available (e.g.,on the internet, for example at invitrogen.com).

It is not necessary for all positions in a given oligonucleotide to beuniformly modified, and in fact more than one of the aforementionedmodifications may be incorporated in a single oligonucleotide or even atwithin a single nucleoside within an oligonucleotide.

In some embodiments, the oligonucleotides are chemically linked to oneor more moieties or conjugates that enhance the activity, cellulardistribution, or cellular uptake of the oligonucleotide. Such moietiescomprise but are not limited to, lipid moieties such as a cholesterolmoiety (Letsinger et al., Proc. Natl. Acad. Sci. USA, 1989, 86,6553-6556), cholic acid (Manoharan et al., Bioorg. Med. Chem. Let.,1994, 4, 1053-1060), a thioether, e.g., hexyl-S-tritylthiol (Manoharanet al, Ann. N. Y. Acad. Sci., 1992, 660, 306-309; Manoharan et al.,Bioorg. Med. Chem. Let., 1993, 3, 2765-2770), a thiocholesterol(Oberhauser et al., Nucl. Acids Res., 1992, 20, 533-538), an aliphaticchain, e.g., dodecandiol or undecyl residues (Kabanov et al., FEBSLett., 1990, 259, 327-330; Svinarchuk et al., Biochimie, 1993, 75,49-54), a phospholipid, e.g., di-hexadecyl-rac-glycerol ortriethylammonium 1,2-di-O-hexadecyl-rac-glycero-3-H-phosphonate(Manoharan et al., Tetrahedron Lett., 1995, 36, 3651-3654; Shea et al.,Nucl. Acids Res., 1990, 18, 3777-3783), a polyamine or a polyethyleneglycol chain (Mancharan et al., Nucleosides & Nucleotides, 1995, 14,969-973), or adamantane acetic acid (Manoharan et al., TetrahedronLett., 1995, 36, 3651-3654), a palmityl moiety (Mishra et al., Biochim.Biophys. Acta, 1995, 1264, 229-237), or an octadecylamine orhexylamino-carbonyl-t oxycholesterol moiety (Crooke et al., J.Pharmacol. Exp. Ther., 1996, 277, 923-937). See also U.S. Pat. Nos.4,828,979; 4,948,882; 5,218,105; 5,525,465; 5,541,313; 5,545,730; 5,552,538; 5,578,717, 5,580,731; 5,580,731; 5,591,584; 5,109,124; 5,118,802;5,138,045; 5,414,077; 5,486, 603; 5,512,439; 5,578,718; 5,608,046;4,587,044; 4,605,735; 4,667,025; 4,762, 779; 4,789,737; 4,824,941;4,835,263; 4,876,335; 4,904,582; 4,958,013; 5,082, 830; 5,112,963;5,214,136; 5,082,830; 5,112,963; 5,214,136; 5, 245,022; 5,254,469;5,258,506; 5,262,536; 5,272,250; 5,292,873; 5,317,098; 5,371,241, 5,391,723; 5,416,203, 5,451,463; 5,510,475; 5,512,667; 5,514,785; 5, 565,552;5,567,810; 5,574,142; 5,585,481; 5,587,371; 5,595,726; 5,597,696;5,599,923; 5,599, 928 and 5,688,941, each of which is hereinincorporated by reference.

These moieties or conjugates can include conjugate groups covalentlybound to functional groups such as primary or secondary hydroxyl groups.Conjugate groups of the invention include intercalators, reportermolecules, polyamines, polyamides, polyethylene glycols, polyethers,groups that enhance the pharmacodynamic properties of oligomers, andgroups that enhance the pharmacokinetic properties of oligomers. Typicalconjugate groups include cholesterols, lipids, phospholipids, biotin,phenazine, folate, phenanthridine, anthraquinone, acridine,fluoresceins, rhodamines, coumarins, and dyes. Groups that enhance thepharmacodynamic properties, in the context of this invention, includegroups that improve uptake, enhance resistance to degradation, and/orstrengthen sequence-specific hybridization with the target nucleic acid.Groups that enhance the pharmacokinetic properties, in the context ofthis invention, include groups that improve uptake, distribution,metabolism or excretion of the compounds of the present invention.Representative conjugate groups are disclosed in International PatentApplication No. PCT/US92/09196, filed Oct. 23, 1992, and U.S. Pat. No.6,287,860, which are incorporated herein by reference. Conjugatemoieties include, but are not limited to, lipid moieties such as acholesterol moiety, cholic acid, a thioether, e.g., hexyl-5-tritylthiol,a thiocholesterol, an aliphatic chain, e.g., dodecandiol or undecylresidues, a phospholipid, e.g., di-hexadecyl-rac-glycerol ortriethylammonium 1,2-di-O-hexadecyl-rac-glycero-3-H-phosphonate, apolyamine or a polyethylene glycol chain, or adamantane acetic acid, apalmityl moiety, or an octadecylamine or hexylamino-carbonyl-oxycholesterol moiety. See, e.g., U.S. Pat. Nos. 4,828,979; 4,948,882;5,218,105; 5,525,465; 5,541,313; 5,545,730; 5,552,538; 5,578,717,5,580,731; 5,580,731; 5,591,584; 5,109,124; 5,118,802; 5,138,045;5,414,077; 5,486,603; 5,512,439; 5,578,718; 5,608,046; 4,587,044;4,605,735; 4,667,025; 4,762,779; 4,789,737; 4,824,941; 4,835,263;4,876,335; 4,904,582; 4,958,013; 5,082,830; 5,112,963; 5,214,136;5,082,830; 5,112,963; 5,214,136; 5,245,022; 5,254,469; 5,258,506;5,262,536; 5,272,250; 5,292,873; 5,317,098; 5,371,241, 5,391,723;5,416,203, 5,451,463; 5,510,475; 5,512,667; 5,514,785; 5,565,552;5,567,810; 5,574,142; 5,585,481; 5,587,371; 5,595,726; 5,597,696;5,599,923; 5,599,928 and 5,688,941.

In general, the oligonucleotides useful in the methods described hereinare at least 80% identical to the miRNA, e.g., 90%, 95%, or 100%sequence identity to the miRNA. For example, an oligonucleotide compoundin which 18 of 20 nucleobases of the oligonucleotide are identical to areference miRNA sequence would represent 90 percent identity. Percentidentity of an oligonucleotides with a miRNA can be determined routinelyusing basic local alignment search tools (BLAST programs) (Altschul etal., J. Mol. Biol., 1990, 215, 403-410; Zhang and Madden, Genome Res.,1997, 7, 649-656). Useful oligonucleotides can be identified throughroutine experimentation. In general the oligonucleotides must retainspecificity for their target, i.e., must not directly bind to, ordirectly significantly affect expression levels of, transcripts otherthan the intended target.

For further disclosure regarding oligonucleotides, please seeUS2010/0249052 (double-stranded ribonucleic acid (dsRNA));US2009/0181914 and US2010/0234451 (LNAs); US2007/0191294 (siRNAanalogues); US2008/0249039 (modified siRNA); and WO2010/129746 andWO2010/040112 (inhibitory nucleic acids).

Making and Using Oligonucleotides

The nucleic acid sequences used to practice the methods describedherein, whether RNA, DNA, vectors, viruses or hybrids thereof, can beisolated from a variety of sources, genetically engineered, amplified,and/or expressed or generated recombinantly. Recombinant nucleic acidsequences can be individually isolated or cloned and tested for adesired activity. Any recombinant expression system can be used,including e.g. in vitro, bacterial, fungal, mammalian, yeast, insect orplant cell expression systems.

The miR-17-92 oligonucleotides can be inserted into delivery vectors andexpressed from transcription units within the vectors. The recombinantvectors can be DNA plasmids or viral vectors. Generation of the vectorconstruct can be accomplished using any suitable genetic engineeringtechniques well known in the art, including, without limitation, thestandard techniques of PCR, oligonucleotide synthesis, restrictionendonuclease digestion, ligation, transformation, plasmid purification,and DNA sequencing, for example as described in Sambrook et al.Molecular Cloning: A Laboratory Manual. (1989)), Coffin et al.(Retroviruses. (1997)) and “RNA Viruses: A Practical Approach” (Alan J.Cann, Ed., Oxford University Press, (2000)). As will be apparent to oneof ordinary skill in the art, a variety of suitable vectors areavailable for transferring nucleic acids of the invention into cells.The selection of an appropriate vector to deliver nucleic acids andoptimization of the conditions for insertion of the selected expressionvector into the cell, are within the scope of one of ordinary skill inthe art without the need for undue experimentation. Viral vectorscomprise a nucleotide sequence having sequences for the production ofrecombinant virus in a packaging cell. Viral vectors expressing nucleicacids of the invention can be constructed based on viral backbonesincluding, but not limited to, a retrovirus, lentivirus, adenovirus,adenoassociated virus, pox virus or alphavirus. The recombinant vectorscapable of expressing the nucleic acids of the invention can bedelivered as described herein, and persist in target cells (e.g., stabletransformants).

Nucleic acid sequences used to practice this invention can besynthesized in vitro by well-known chemical synthesis techniques, asdescribed in, e.g., Adams (1983) J. Am. Chem. Soc. 105:661; Belousov(1997) Nucleic Acids Res. 25:3440-3444; Frenkel (1995) Free Radic. Biol.Med. 19:373-380; Blommers (1994) Biochemistry 33:7886-7896; Narang(1979) Meth. Enzymol. 68:90; Brown (1979) Meth. Enzymol. 68:109;Beaucage (1981) Tetra. Lett. 22:1859; U.S. Pat. No. 4,458,066.

Techniques for the manipulation of nucleic acids used to practice thisinvention, such as, e.g., subcloning, labeling probes (e.g.,random-primer labeling using Klenow polymerase, nick translation,amplification), sequencing, hybridization and the like are welldescribed in the scientific and patent literature, see, e.g., Sambrooket al., Molecular Cloning; A Laboratory Manual 3d ed. (2001); CurrentProtocols in Molecular Biology, Ausubel et al., eds. (John Wiley & Sons,Inc., New York 2010); Kriegler, Gene Transfer and Expression: ALaboratory Manual (1990); Laboratory Techniques In Biochemistry AndMolecular Biology: Hybridization With Nucleic Acid Probes, Part I.Theory and Nucleic Acid Preparation, Tijssen, ed. Elsevier, N.Y. (1993).

Pharmaceutical Compositions

The methods described herein can include the administration ofpharmaceutical compositions and formulations comprising miR-17-92oligonucleotides.

In some embodiments, the compositions are formulated with apharmaceutically acceptable carrier. The pharmaceutical compositions andformulations can be administered parenterally, topically, orally or bylocal administration, such as by aerosol or transdermally. Thepharmaceutical compositions can be formulated in any way and can beadministered in a variety of unit dosage forms depending upon thecondition or disease and the degree of illness, the general medicalcondition of each patient, the resulting preferred method ofadministration and the like. Details on techniques for formulation andadministration of pharmaceuticals are well described in the scientificand patent literature, see, e.g., Remington: The Science and Practice ofPharmacy, 21st ed., 2005.

The oligonucleotides can be administered alone or as a component of apharmaceutical formulation (composition). The compounds may beformulated for administration, in any convenient way for use in human orveterinary medicine. Wetting agents, emulsifiers and lubricants, such assodium lauryl sulfate and magnesium stearate, as well as coloringagents, release agents, coating agents, sweetening, flavoring andperfuming agents, preservatives and antioxidants can also be present inthe compositions.

Formulations of the compositions of the invention include those suitablefor intradermal, inhalation, oral/nasal, topical, parenteral, rectal,and/or intravaginal administration. The formulations may conveniently bepresented in unit dosage form and may be prepared by any methods wellknown in the art of pharmacy. The amount of active ingredient (e.g.,nucleic acid sequences of this invention) which can be combined with acarrier material to produce a single dosage form will vary dependingupon the host being treated, the particular mode of administration,e.g., intradermal or inhalation. The amount of active ingredient whichcan be combined with a carrier material to produce a single dosage formwill generally be that amount of the compound which produces atherapeutic effect.

Pharmaceutical formulations of this invention can be prepared accordingto any method known to the art for the manufacture of pharmaceuticals. Aformulation can be admixtured with nontoxic pharmaceutically acceptableexcipients which are suitable for manufacture. Formulations may compriseone or more diluents, emulsifiers, preservatives, buffers, excipients,etc. and may be provided in such forms as liquids, powders, emulsions,lyophilized powders, sprays, controlled release formulations, tablets,pills, gels, on patches, in implants, etc.

Pharmaceutical formulations for oral administration can be formulatedusing pharmaceutically acceptable carriers well known in the art inappropriate and suitable dosages. Such carriers enable thepharmaceuticals to be formulated in unit dosage forms as tablets, pills,powder, dragees, capsules, liquids, lozenges, gels, syrups, slurries,suspensions, etc., suitable for ingestion by the patient. Pharmaceuticalpreparations for oral use can be formulated as a solid excipient,optionally grinding a resulting mixture, and processing the mixture ofgranules, after adding suitable additional compounds, if desired, toobtain tablets or dragee cores. Suitable solid excipients arecarbohydrate or protein fillers include, e.g., sugars, includinglactose, sucrose, mannitol, or sorbitol; starch from corn, wheat, rice,potato, or other plants; cellulose such as methyl cellulose,hydroxypropylmethyl-cellulose, or sodium carboxy-methylcellulose; andgums including arabic and tragacanth; and proteins, e.g., gelatin andcollagen. Disintegrating or solubilizing agents may be added, such asthe cross-linked polyvinyl pyrrolidone, agar, alginic acid, or a saltthereof, such as sodium alginate. Push-fit capsules can contain activeagents mixed with a filler or binders such as lactose or starches,lubricants such as talc or magnesium stearate, and, optionally,stabilizers. In soft capsules, the active agents can be dissolved orsuspended in suitable liquids, such as fatty oils, liquid paraffin, orliquid polyethylene glycol with or without stabilizers.

Aqueous suspensions can contain an active agent (e.g., nucleic acidsequences of the invention) in admixture with excipients suitable forthe manufacture of aqueous suspensions, e.g., for aqueous intradermalinjections. Such excipients include a suspending agent, such as sodiumcarboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose,sodium alginate, polyvinylpyrrolidone, gum tragacanth and gum acacia,and dispersing or wetting agents such as a naturally occurringphosphatide (e.g., lecithin), a condensation product of an alkyleneoxide with a fatty acid (e.g., polyoxyethylene stearate), a condensationproduct of ethylene oxide with a long chain aliphatic alcohol (e.g.,heptadecaethylene oxycetanol), a condensation product of ethylene oxidewith a partial ester derived from a fatty acid and a hexitol (e.g.,polyoxyethylene sorbitol mono-oleate), or a condensation product ofethylene oxide with a partial ester derived from fatty acid and ahexitol anhydride (e.g., polyoxyethylene sorbitan mono-oleate). Theaqueous suspension can also contain one or more preservatives such asethyl or n-propyl p-hydroxybenzoate, one or more coloring agents, one ormore flavoring agents and one or more sweetening agents, such assucrose, aspartame or saccharin. Formulations can be adjusted forosmolarity.

In some embodiments, oil-based pharmaceuticals are used foradministration of nucleic acid sequences of the invention. Oil-basedsuspensions can be formulated by suspending an active agent in avegetable oil, such as arachis oil, olive oil, sesame oil or coconutoil, or in a mineral oil such as liquid paraffin; or a mixture of these.See e.g., U.S. Pat. No. 5,716,928 describing using essential oils oressential oil components for increasing bioavailability and reducinginter- and intra-individual variability of orally administeredhydrophobic pharmaceutical compounds (see also U.S. Pat. No. 5,858,401).The oil suspensions can contain a thickening agent, such as beeswax,hard paraffin or cetyl alcohol. Sweetening agents can be added toprovide a palatable oral preparation, such as glycerol, sorbitol orsucrose. These formulations can be preserved by the addition of anantioxidant such as ascorbic acid. As an example of an injectable oilvehicle, see Minto (1997) J. Pharmacol. Exp. Ther. 281:93-102.

Pharmaceutical formulations can also be in the form of oil-in-wateremulsions. The oily phase can be a vegetable oil or a mineral oil,described above, or a mixture of these. Suitable emulsifying agentsinclude naturally-occurring gums, such as gum acacia and gum tragacanth,naturally occurring phosphatides, such as soybean lecithin, esters orpartial esters derived from fatty acids and hexitol anhydrides, such assorbitan mono-oleate, and condensation products of these partial esterswith ethylene oxide, such as polyoxyethylene sorbitan mono-oleate. Theemulsion can also contain sweetening agents and flavoring agents, as inthe formulation of syrups and elixirs. Such formulations can alsocontain a demulcent, a preservative, or a coloring agent. In alternativeembodiments, these injectable oil-in-water emulsions of the inventioncomprise a paraffin oil, a sorbitan monooleate, an ethoxylated sorbitanmonooleate and/or an ethoxylated sorbitan trioleate.

In some embodiments, the oligonucleotides are prepared foradministration by mixing with a reagent that enhances delivery, e.g.,atelocollagen; INVIVOFECTAMINE, an animal-origin-free lipid based invivo RNA delivery reagent (Invitrogen); or NLE, which consists of1,2-dioleoyl-sn-glycero-3-phosphocholine, squalene oil, polysorbate 20,and an antioxidant that forms nanoparticle complexes with syntheticmiRNAs in the nanometer diameter range (see, e.g., Trang et al., MolTher. 2011 June; 19(6): 1116-22).

The pharmaceutical compounds can also be administered by in intranasal,intraocular and intravaginal routes including suppositories,insufflation, powders and aerosol formulations (for examples of steroidinhalants, see e.g., Rohatagi (1995) J. Clin. Pharmacol. 35:1187-1193;Tjwa (1995) Ann. Allergy Asthma Immunol. 75:107-111). Suppositoriesformulations can be prepared by mixing the drug with a suitablenon-irritating excipient which is solid at ordinary temperatures butliquid at body temperatures and will therefore melt in the body torelease the drug. Such materials are cocoa butter and polyethyleneglycols.

In some embodiments, the pharmaceutical compounds can be deliveredtransdermally, by a topical route, formulated as applicator sticks,solutions, suspensions, emulsions, gels, creams, ointments, pastes,jellies, paints, powders, and aerosols.

In some embodiments, the pharmaceutical compounds can also be deliveredas microspheres for slow release in the body. For example, microspherescan be administered via intradermal injection of drug which slowlyrelease subcutaneously; see Rao (1995) J. Biomater Sci. Polym. Ed.7:623-645; as biodegradable and injectable gel formulations, see, e.g.,Gao (1995) Pharm. Res. 12:857-863 (1995); or, as microspheres for oraladministration, see, e.g., Eyles (1997) J. Pharm. Pharmacol. 49:669-674.

In some embodiments, the pharmaceutical compounds can be parenterallyadministered, such as by intravenous (IV) administration,intraperitoneal (IP) administration or administration into a body cavityor lumen of an organ. These formulations can comprise a solution ofactive agent dissolved in a pharmaceutically acceptable carrier.Acceptable vehicles and solvents that can be employed are water andRinger's solution, an isotonic sodium chloride. In addition, sterilefixed oils can be employed as a solvent or suspending medium. For thispurpose any bland fixed oil can be employed including synthetic mono- ordiglycerides. In addition, fatty acids such as oleic acid can likewisebe used in the preparation of injectables. These solutions are sterileand generally free of undesirable matter. These formulations may besterilized by conventional, well known sterilization techniques. Theformulations may contain pharmaceutically acceptable auxiliarysubstances as required to approximate physiological conditions such aspH adjusting and buffering agents, toxicity adjusting agents, e.g.,sodium acetate, sodium chloride, potassium chloride, calcium chloride,sodium lactate and the like. The concentration of active agent in theseformulations can vary widely, and will be selected primarily based onfluid volumes, viscosities, body weight, and the like, in accordancewith the particular mode of administration selected and the patient'sneeds. For IV or IP administration, the formulation can be a sterileinjectable preparation, such as a sterile injectable aqueous oroleaginous suspension. This suspension can be formulated using thosesuitable dispersing or wetting agents and suspending agents. The sterileinjectable preparation can also be a suspension in a nontoxicparenterally-acceptable diluent or solvent, such as a solution of1,3-butanediol. The administration can be by bolus or continuousinfusion (e.g., substantially uninterrupted introduction into a bloodvessel for a specified period of time).

In some embodiments, the pharmaceutical compounds and formulations canbe lyophilized. Stable lyophilized formulations comprisingoligonucleotides as described herein can be made by lyophilizing asolution comprising a pharmaceutical of the invention and a bulkingagent, e.g., mannitol, trehalose, raffinose, and sucrose or mixturesthereof. See, e.g., U.S. 20040028670.

The compositions and formulations can be delivered by the use ofliposomes. By using liposomes, particularly where the liposome surfacecarries ligands specific for target cells, or are otherwisepreferentially directed to a specific organ, one can focus the deliveryof the active agent into target cells in vivo. See, e.g., U.S. Pat. Nos.6,063,400; 6,007,839; Al-Muhammed (1996) J. Microencapsul. 13:293-306;Chonn (1995) Curr. Opin. Biotechnol. 6:698-708; Ostro (1989) Am. J.Hosp. Pharm. 46:1576-1587. Liposomes (e.g., as described in U.S. Pat.No. 6,472,375) and microencapsulation can also be used. Biodegradabletargetable microparticle delivery systems can also be used (e.g., asdescribed in U.S. Pat. No. 6,471,996).

The formulations of the invention can be administered for prophylacticand/or therapeutic treatments. In some embodiments, for therapeuticapplications, compositions are administered to a subject who is in needof cardiomyocyte proliferation, e.g., who has had an cardiac injury,e.g., ischemic, e.g., after myocardial infarction (MI); an injury to theheart, e.g., as a result of cardiotoxic drugs (e.g., anthracyclineantibiotics (e.g., doxorubicin), cocaine, methamphetamine, cyclicantidepressants, calcium channel blockers, beta-blockers, and digoxin)or trauma (whether accidental or intentional as a result of surgery);heart failure; or diminished cardiac capacity associated with normalaging; or who is at risk of or has a disorder described herein, in anamount sufficient to cure, alleviate or partially arrest the clinicalmanifestations of the disorder or its complications; this can be calleda therapeutically effective amount. For example, in some embodiments,pharmaceutical compositions of the invention are administered in anamount sufficient to improve cardiac function, increase cardiaccontractile force, or increase the thickness of the myocardium in thesubject.

The amount of pharmaceutical composition adequate to accomplish this isa therapeutically effective dose. The dosage schedule and amountseffective for this use, i.e., the dosing regimen, will depend upon avariety of factors, including the stage of the disease or condition, theseverity of the disease or condition, the general state of the patient'shealth, the patient's physical status, age and the like. In calculatingthe dosage regimen for a patient, the mode of administration also istaken into consideration.

The dosage regimen also takes into consideration pharmacokineticsparameters well known in the art, i.e., the active agents' rate ofabsorption, bioavailability, metabolism, clearance, and the like (see,e.g., Hidalgo-Aragones (1996) J. Steroid Biochem. Mol. Biol. 58:611-617;Groning (1996) Pharmazie 51:337-341; Fotherby (1996) Contraception54:59-69; Johnson (1995) J. Pharm. Sci. 84:1144-1146; Rohatagi (1995)Pharmazie 50:610-613; Brophy (1983) Eur. J. Clin. Pharmacol. 24:103-108;Remington: The Science and Practice of Pharmacy, 21st ed., 2005). Thestate of the art allows the clinician to determine the dosage regimenfor each individual patient, active agent and disease or conditiontreated. Guidelines provided for similar compositions used aspharmaceuticals can be used as guidance to determine the dosageregiment, i.e., dose schedule and dosage levels, administered practicingthe methods of the invention are correct and appropriate.

Single or multiple administrations of formulations can be givendepending on for example: the dosage and frequency as required andtolerated by the patient, the degree and amount of cardiomyocyteproliferation generated after each administration, i.e., as measured byimproved cardiac function, increased cardiac contractile force, orincreased thickness of the myocardium, and the like. The formulationsshould provide a sufficient quantity of active agent to effectivelytreat, prevent or ameliorate conditions, diseases or symptoms asdescribed herein.

Various studies have reported successful mammalian dosing using nucleicacid sequences. For example, Esau C., et al., (2006) Cell Metabolism,3(2):87-98 reported dosing of normal mice with intraperitoneal doses ofmiR-122 antisense oligonucleotide ranging from 12.5 to 75 mg/kg twiceweekly for 4 weeks. They concluded that 50 mg/kg was an effective,non-toxic dose. Another study by Kruitzfeldt J., et al., (2005) Nature438, 685-689, injected anatgomirs to silence miR-122 in mice using atotal dose of 80, 160 or 240 mg per kg body weight. The highest doseresulted in a complete loss of miR-122 signal. In yet another study,locked nucleic acids (“LNAs”) were successfully applied in primates tosilence miR-122. Elmen J., et al., (2008) Nature 452, 896-899, reportthat efficient silencing of miR-122 was achieved in primates by threedoses of 10 mg kg⁻¹ LNA-antimiR, leading to a long-lasting andreversible decrease in total plasma cholesterol without any evidence forLNA-associated toxicities or histopathological changes in the studyanimals.

In some embodiments, the methods described herein can includeco-administration with other drugs or pharmaceuticals, e.g.,compositions for providing cholesterol homeostasis. For example, theoligonucleotides can be co-administered with cardiac progenitor or stemcells (e.g., as described in Boyle et al., Circulation. 2006; 114:339-352; or with oligonucleotides comprising hsa-miR-590 and/orhsa-miR-199a (e.g., as described in Eulalio et al., 2012, supra), fortreating or reducing risk of a disorder described herein.

EXAMPLES

The invention is further described in the following examples, which donot limit the scope of the invention described in the claims.

Materials and Methods

The following materials and methods were used in examples 1-5 describedherein.

Animals

All experiments with mice were performed according to protocols approvedby the Institutional Animal Care and Use Committees of Boston Children'sHospital. miR-17-92^(flox/flox) (Ventura A, et al. (2008) Targeteddeletion reveals essential and overlapping functions of the miR-17through 92 family of miRNA clusters. Cell 132:875-886),miR-17-92^(TG/TG) (Xiao C, et al. (2008) Lymphoproliferative disease andautoimmunity in mice with increased miR-17-92 expression in lymphocytes.Nat Immunol 9:405-414), Nkx2-5^(Cre/+) (Moses K A, DeMayo F, Braun R M,Reecy J L, Schwartz R J (2001) Embryonic expression of an Nkx2-5/Cregene using ROSA26 reporter mice. Genesis 31:176-180), αMHC-Cre (Oka T,et al. (2006) Cardiac-specific deletion of Gata4 reveals its requirementfor hypertrophy, compensation, and myocyte viability. Circ Res98:837-845), αMHC-MerCreMer (Sohal D S, et al. (2001) Temporallyregulated and tissue-specific gene manipulations in the adult andembryonic heart using a tamoxifen-inducible Cre protein. Circ Res89:20-25) were described previously.

Cardiac-Specific Knockout of miR-17-92 Cluster in Mice

The miR-17-92^(flox/+) mice harbor an allele of loxP-flanked miR-17-92cluster. miR-17-92^(flox/flox) mice were crossed with Nkx2-5^(Cre/+)mice, in which the expression of Cre recombinase is controlled by theendogenous promoter of cardiac-specific marker gene, Nkx2-5, to generatethe miR-17-92^(F/+); Nkx2-5^(Cre/+) offsprings. The miR-17-92^(flox/+);Nkx2-5^(Cre/+) mice were then crossed back to miR-17-92^(flox/flox) miceto obtain the miR-17-92 conditional (cardiac-specific) knockout (cKO)mice (miR-17-92^(flox/flox); Nkx2-5^(Cre/+)).

Cardiac-Specific Overexpression of miR-17-92 Cluster in Mice

miR-17-92^(TG/+) mice harbor the miR-17-92 transgene targeted to theGt(ROSA)26Sor locus. The miR-17-92 transgene has a loxP-flanked Neo-STOPcassette preventing transcription of the downstream human miR-17-92cluster. When bred to mice that express Cre recombinase, the resultingoffspring will have the STOP cassette deleted in the Cre-expressingtissue resulting in ectopic expression of the miR-17-92 cluster.miR-17-92^(TG/+) mice were crossed with Nkx2-5^(Cre/+) mice and αMHC-Cremice, respectively, to obtain the miR-17-92^(TG/+); Nkx2-5^(Cre/+)offsprings and miR-17-92^(TG/+); αMHC-Cre offsprings. miR-17-92 clusteris cardiac-specific overexpressed in these offsprings. miR-17-92^(TG/+)mice were crossed with αMHC-MerCreMer (MerCreMer) to obtainmiR-17-92^(TG/+); MerCreMer offsprings for inducible cardiac-specificoverexpression of miR-17-92 cluster. In order to achieve the inductionof overexpression, tamoxifen was administrated in these mice. EdU wasadministered intraperitoneally at 5 μg per g of body weight (adult), 6times for continuous day.

Ischemic Injury Model—Myocardial Infarction (MI)

Myocardial infarction (MI) was induced by ligation of left anteriordescending coronary artery. 8 week old male C57 mice were randomlyselected to undergo coronary artery ligation or sham surgery. Forsurgery, mice were anesthetized with isoflurane (3% isoflurane forinduction, 2% isoflurane for maintenance). The chest was shaved andcleaned with alcohol. A suture was placed around the front upperincisors and pulled taut so that the neck was slightly extended. Thetongue was retracted and held with forceps, and a 20-G catheter wasinserted into the trachea. The catheter was then attached to the mouseventilator via a Y-shaped connector. Ventilation was performed with atidal volume of 225 μl for a 25 g mouse and a respiratory rate of 130breaths/min. 100% oxygen was provided to the inflow of the ventilator.The chest was opened through a left parasternal incision, and the heartexposed at the left 3rd-4th intercostal space. Chest retractor wasapplied to facilitate the view. The pericardium was opened, andligations made on the left anterior descending coronary artery (LAD)using 8-0 silk sutures (Ethicon). The lungs were slightly overinflatedto assist in removal of air in the pleural cavity.

All mice were given a single dose of 10 g synthetic microRNA-19a/b(Dharmacon, Lafayette, Colo.) (miR-19a: UGUGCAAAUCUAUGCAAAACUGA (SEQ IDNO:1; miR-19b: UGUGCAAAUCCAUGCAAAACUGA; SEQ ID NO:3) formulated with NLEaccording to the manufacturer's instructions by intra-myocardiuminjection. The NLE (MaxSuppressor in vivo RNALancerII) was purchasedfrom BIOO Scientific, (Austin, Tex.). NLE consists of1,2-dioleoyl-sn-glycero-3-phosphocholine, squalene oil, polysorbate 20,and an antioxidant that forms nanoparticle complexes with syntheticmiRNAs in the nanometer diameter range.

Sham operations were performed similarly, but without ligation of theartery. The chest cavity was closed with 6-0 silk sutures (Ethicon), theskin incision was closed by liquid topical adhesive (Nexaband),anesthesia was discontinued, and the animal was observed untilconscious. The duration of each procedure was about 15-20 mins.Postoperative analgesics (0.05-0.1 mg/kg Buprenorphine s.c.) ware givenevery 8-12 h for 48 hours. About 6-15 mice ware used for eachexperimental group.

Measurement of Cardiac Function by Echocardiography

Echocardiographic measurements were performed on mice using a VisualSonics Vevo® 2100 Imaging System (Visual Sonics, Toronto, Canada) with a40 MHz MicroScan transducer (model MS-550D). Mice were anesthetized withisoflurane (2.5% isoflurane for induction and 0.5% for maintenance).Heart rate and left ventricular (LV) dimensions, including diastolic andsystolic wall thicknesses, LV end-diastolic and end-systolic chamberdimensions were measured from 2-D short-axis under M-mode tracings atthe level of the papillary muscle. LV mass and functional parameterssuch as percentage of fractional shortening (FS %) and left ventricularvolume were calculated using the above primary measurements andaccompanying software.

Modified RNA (ModRNA)

The modified RNA (ModRNA) experiment was performed essentially asdescribed (Warren L, et al. (2010) Highly efficient reprogramming topluripotency and directed differentiation of human cells with syntheticmodified mRNA. Cell Stem Cell 7:618-630). Briefly, the “universal”ModRNA backbone was generated by modifying previously describedpcDNA3.3-TOPO-cMyc ORF plasmid containing T7 promoter and optimized 5′and 3′ untranslated regions (pcDNA3.3-TOPO-T7-5′UTR-cMyc-3′UTR,). ThepcDNA3.3-TOPO backbone with 5′/3′UTRs (pcDNA3.3-TOPO-5′3′UTRs) wasamplified by long-range PCR (PrimeStar high fidelity DNA polymerase,Takara). Two unique restriction sites for AscI and NheI wereincorporated into the PCR products, in order to create the 5′ and 3′sticky ends. The ORF of PTEN cDNA was PCR amplified and first clonedinto the pcDNA3-N-Flag vector. The fusion Flag-PTEN ORF was thenamplified using forward primer containing NheI site and reverse primerwith AscI site, and sub-cloned into the pcDNA3.3-TOPO-5′ and 3′UTRsbackbone to generate the pcDNA3.3-TOPO-T7-5′UTR-Flag-PTEN-3′UTR.

Cardiomyocyte Isolation and Culture

Neonatal rat and mouse cardiomyocytes were prepared as previouslydescribed (Tatsuguchi M, et al. (2007) Expression of microRNAs isdynamically regulated during cardiomyocyte hypertrophy. J Mol CellCardiol 42:1137-1141). Briefly, Neonatal rat and mouse cardiomyocyteswere isolated by enzymatic disassociation of one day-old or four day-old(P1 or P4) neonate hearts with the Neonatal Cardiomyocyte Isolation Kit(Cellutron, Baltimore Md.). Cardiomyocytes were plated differentiallyfor 2 hours to remove fibroblasts. Cells were plated on 1% gelatincoated plates in medium containing 10% horse serum and 5% fetal calfserum (FCS). After 24 hours of plating, cells were changed intoserum-free medium overnight. Then, 100 nM of microRNA mimic duplex or200 nM microRNA hairpin inhibitors of miR-17-92 cluster members andnegative control oligonucleotide (Dharmacon) were transfected intocardiomyocyte by using Lipofectamine RNAiMAX (Invitrogen) transfectionreagent. After 6 hours transfection, the cultures were changed to serumfree medium for mimic experiments and changed to 1% FCS medium forinhibitor experiments. EdU (5-ethynyl-2′-deoxyuridine, Invitrogen) wasadded, 24 hours later, cells were fixed and harvested for Q-PCR analysesand immunohistochemistry analyses.

Adult mouse cardiomyocyte were isolated using a previously describedprocedure (O'Connell T D, et al. (2006) Alpha1-adrenergic receptorsprevent a maladaptive cardiac response to pressure overload. J ClinInvest 116:1005-1015) with minor modifications. Briefly, followingperfusion and digestion of the heart with collagenase II (WorthingtonBiochemical Corp, Lakewood, N.J.), dissociated cells (myocytes andnon-myocytes) were sedimented by gravity. The bottom layer is rich inadult cardiomyocyte for cell counting and staining.

Quantitative RT-PCR

Total RNAs were isolated using Trizol Reagent (Invitrogen) from cell ortissue samples. For quantitative RT-PCR detecting the expression ofprotein-coding gene, 2.0 μg RNA samples were reverse-transcribed to cDNAusing random hexamers and MMLV reverse transcriptase (Invitrogen) in 20μl reaction system. In each analysis, 0.1 μl cDNA pool was used forquantitative PCR. For quantitative RT-PCR detecting the expression ofmiRNAs, 10 ng RNA samples were reverse-transcribed to cDNA by usingTaqMan® MicroRNA Reverse Transcription Kit (ABI). In each analysis, 1.5μl cDNA pool and TaqMan® MicroRNA Assays were used for quantitative PCR.For target gene expression, Real time PCR was performed with SYBR Greendetection. All qPCR experiments were performed on the Applied Biosystems7500 Real-Time PCR System.

Histology and Immunostaining

Mouse hearts were dissected out, rinsed with PBS and fixed in 4%paraformaldehyde (pH 8.0) overnight. After dehydration through a seriesof ethanol baths, samples were embedded in paraffin wax according tostandard laboratory procedures. Sections of 5 μm were stained withHaematoxylin and Eosin (H&E) for routine histological examination withlight microscope.

To determine infarct size, hearts were fixed in 4% PFA, dehydrated andembedded in paraffin. Then the embedded paraffin blocks were cut throughfrom apex to base. The first 10 sections (10 μm thickness each) of every100 sections were used. Sections were stained with Sirius Red-FastGreen. Infarct size was calculated according to the formula:[length of coronal infarct perimeter (epicardial+endocardial)/total leftventricle coronal perimeter (epicardial+endocardial)]×100(Pfeffer J M, Pfeffer M A, Fletcher P J, Braunwald E (1991) Progressiveventricular remodeling in rat with myocardial infarction. Am J Physiol260:H1406-1414).

Immunofluorescence was performed on paraformaldehyde (PFA)-fixed,paraffin-embedded heart sections. After deparaffinization,re-hydratation and

heat-induced epitope retrieval, sections were incubated with antibodies,rabbit phospho-Histone H3 (pH3, 1:400, Millipore, cat #06-570),anti-mouse α-actinin (ACTN1, 1:250, Abcam, cat#ab9465) and goatanti-rabbit AlexaFluor 488 and goat anti-mouse AlexaFluor 594 secondaryantibody (1:400, Invitrogen). Images were captured using confocalmicroscopy

(FV1000, Olympus). Quantitative data were obtained by measuringco-localization of 4′,6-diamidino-2-phenylindole DAPI (nuclear staining)with pH3 in the cardiomyocyte area. EdU was detected with Click-iTchemistry (Invitrogen). Imaging was performed on a Nikon TE2000epifluorescent microscope with deconvolution (Volocity; Perkin-Elmer) oron an Olympus FV1000 confocal.

Statistics

Values are reported as means±SEM unless indicated otherwise. The2-tailed Mann-Whitney U test was used for comparing 2 means (Prism,GraphPad). Values of P<0.05 were considered statistically significant.

Example 1. miR-17-92 is Required for Cardiomyocyte Proliferation inEmbryonic and Postnatal Hearts

miR-17-92^(flox/flox) mice¹⁵ were crossed with Nkx2.5-Cre mice, in whichthe expression of Cre recombinase was under the control of thecardiac-specific Nkx2.5 gene, to delete miR-17-92 in embryonic,postnatal and adult hearts (FIG. 1j ). Cardiac-specific miR-17-92 mutantmice (named miR-17-92-cKO) ware slightly under-representative at weaningage (20.3%), suggesting that cardiac-specific deletion of miR-17-92resulted in partial embryonic lethality (FIG. 1k ). The expression ofmiR-17-92 miRNAs was significantly reduced in the hearts of mutant mice(FIG. 1i ).

The hearts of postnatal miR-17-92-cKO mice were substantially smallerthan that of their littermate controls (FIG. 1a ). The proliferation ofcardiomyocytes was examined in miR-17-92-cKO hearts, usingimmunostaining for phosphorylated histone H3 (pH3) which marks mitosis.There was less proliferating cardiomyocytes in postnatal hearts ofmiR-17-92-cKO mice (FIG. 1b, c ). Quantitative analyses confirmedsubstantial decrease in total numbers of pH3 positive cardiomyocytes inmiR-17-92-cKO hearts (FIG. 1d ). A decrease in cardiomyocyteproliferation was also observed in miR-17-92 heterozygous hearts (FIG.1d ).

Most miR-17-92-cKO mice survived to adulthood, so miR-17-92loss-of-function phenotype in adult hearts was investigated. ThemiR-17-92-cKO hearts were smaller than that of their littermate controls(FIG. 1e ). The heart weight (HW) to body weight (BW) ratio was notaltered in miR-17-92-cKO mice (FIG. 1f ). This is likely due acompensatory cardiomyocyte hypertrophy in these hearts (FIG. 1m ). TheLangendorf perfusion method was used to isolate and quantify totalcardiomyocyte numbers from adult hearts; a substantial decrease in thetotal numbers of cardiomyocytes was found in the hearts of miR-17-92-cKOmice (FIG. 1g, h ). Quantitative measurement of the size of isolatedadult cardiomyocytes showed that the size of cardiomyocytes wasincreased in the heart of miR-17-92-cKO mice (FIG. 1i ), consistent withthe idea that increased size of cardiomyocytes compensates for thereduction of total numbers of cardiomyocytes in mutant hearts. Cardiacfunction was examined using echocardiography, and decreased ventriclewall thickness, increased ventricle systolic diameter and decreasedcardiac function were found in miR-17-92-cKO mice when compared withtheir littermate controls (Table 1 and FIG. 1n ). Together, theseresults indicate that miR-17-92 is required for cardiomyocyteproliferation and normal cardiac function in postnatal and adult hearts.

TABLE 1 Table 1. Echocardiography analyses of cardiac function ofdifferent aged cardiac-specific miR- 17-92 knockout mice (cKO,miR-17-92flox/flox; Nkx2-5Cre/+) and their control littermates.2-month-old 6-month-old 13-month-old Control cKO Control cKO Control cKO(N = 6) (N = 6) (N = 6) (N = 5) (N = 6) (N = 6) IVS; d (mm) 0.663 ±0.051 0.616 ± 0.066 0.796 ± 0.117 0.633 ± 0.101* 0.805 ± 0.092 0.693 ±0.067* IVS; s (mm) 1.159 ± 0.172 1.068 ± 0.110 1.172 ± 0.063  0.794 ±0.072** 1.142 ± 0.103  0.853 ± 0.066** LVID; d (mm) 3.361 ± 0.455 3.358± 0.285 3.416 ± 0.305 3.842 ± 0.260* 3.604 ± 0.167 3.555 ± 0.224  LVID;s (mm) 1.606 ± 0.263 1.928 ± 0.325 1.646 ± 0.251  2.420 ± 0.287** 1.715± 0.200  2.259 ± 0.289** LVPW; d (mm) 0.693 ± 0.073 0.756 ± 0.172 0.827± 0.098 0.665 ± 0.074* 0.789 ± 0.097 0.749 ± 0.058  LVPW; s (mm) 1.291 ±0.097 1.251 ± 0.154 1.453 ± 0.171  1.089 ± 0.072** 1.425 ± 0.221 1.115 ±0.101* EF (%) 84.33 ± 2.36  74.62 ± 7.29* 83.69 ± 4.26  67.54 ± 6.05**84.15 ± 3.42  67.25 ± 5.83** FS (%) 52.32 ± 2.58   42.82 ± 6.17** 51.88± 5.09  37.12 ± 4.58** 52.48 ± 4.04  36.69 ± 4.66** LV Mass (mg) 72.14 ±19.24 72.54 ± 20.07 94.22 ± 24.60 83.27 ± 10.80  99.21 ± 17.76 84.88 ±14.39  LV Mass 57.71 ± 15.39 58.03 ± 16.05 75.37 ± 19.68 66.62 ± 8.64 79.36 ± 14.20 67.90 ± 11.52  (Corrected, mg) LV Vol; d (uL) 47.25 ±13.88 46.28 ± 9.64  48.49 ± 10.62 63.95 ± 10.21* 54.72 ± 5.88  53.10 ±7.58  LV Vol; s (uL) 7.55 ± 3.03 12.11 ± 5.18  8.00 ± 3.36 20.99 ±6.22** 8.77 ± 2.51 17.74 ± 4.90** Heart Rate (BMP) 557 ± 30  548 ± 23 572 ± 17  542 ± 26*  559 ± 15  573 ± 57  *P < 0.05; **P < 0.01.

Example 2. miR-17-92 is Sufficient to Induce Cardiomyocyte Proliferationin Embryonic and Postnatal Hearts

Having demonstrated that miR-17-92 is required for cardiomyocyteproliferation in embryonic and postnatal hearts, the next experimentstested whether overexpression of miR-17-92 was sufficient to inducecardiomyocyte proliferation. Cardiac-specific conditional transgenicmice were generated to overexpress miR-17-92 in the heart. The “floxedmiR-17-92 knock-in allele”, in which a loxP-flanked Neo-STOP cassettewas inserted upstream of the bicistronic human miR-17-92 cluster andknocked into the Rosa26 locus (named miR-17-92-KI)¹⁶, were first bredwith the Nkx2.5-Cre mice to achieve the overexpression of miR-17-92 inembryonic and postnatal hearts (FIG. 2f, g ). The hearts ofcardiac-specific miR-17-92 transgenic mice (named miR-17-92-TG^(nkx2.5))were dramatically enlarged (FIG. 2a ). Histological section revealedthat the ventricle wall was substantially thickened in the hearts ofmiR-17-92-TG^(nkx2.5) mice (FIG. 2a ). The heart showed hyperplasia andthe trabeculae were highly condensed and packed (FIG. 2a , lowerpanels). There was no evidence of cardiomyocyte hypertrophy (FIG. 2a ).The increase of cardiomyocyte numbers resulted from an increase incardiomyocyte proliferation.

Phosphorylated histone H3 was used to mark proliferating cardiomyocytes,and overexpression of miR-17-92 was shown to be sufficient to enhancecardiomyocyte proliferation in both embryonic and postnatal hearts (FIG.2 b, c, d). Concordantly, there was a significant increase in heart/bodyweight ratios in the miR-17-92-TG^(nkx2.5) mice (FIG. 2e ).

Next, transgenic mice were generated to overexpress miR-17-92predominantly in postnatal and adult cardiomyocytes. The miR-17-92-KImice were bred with alpha-MHC-Cre transgenic mice, in which theexpression of Cre recombinase was directed by the cardiac-specificalpha-MHC (Myh6) promoter, to generate cardiac-specific miR-17-92transgenic mice (named miR-17-92-TG^(MHC)). About a 2-5 fold increase inmiR-17-92 expression was observed in the transgenic hearts (FIG. 2h ).Most miR-17-92-TG^(MHC) mice survived to adulthood without overtabnormality (Table 2).

TABLE 2 Genotyping results of weaning age mice from intercrossing ofmiR-17- 92^(Tg/TG) and miR-17-92^(TG/+); αMHC-Cre mice. Genotypes miR17-miR17- miR17- 92^(TG/+); miR17- 92^(TG/TG); 92^(TG/+) αMHC-Cre92^(TG/TG) αMHC-Cre Total Number 49 59 58 43 209 Percentage 23.4% 28.2%27.8% 20.6% 100%

The hearts of the miR-17-92-TG^(MHC) mice were substantially enlarged(FIG. 3a ), and the heart/body weight ratio was significantly increasedin these mice (FIG. 3b ). Quantitative measurement of cardiomyocyte cellsize and cell number of the miR-17-92-TG^(MHC) hearts demonstrated asubstantial increase in the cell number in the heart of miR-17-92-TGMmice, whereas the size of cardiomyocyte was not changed (FIGS. 3j, k ).Cardiomyocytes were isolated from adult hearts using the Langendorfisolation method; there was substantial increase in total cardiomyocytenumbers in miR-17-92-TG^(MHC) hearts (FIG. 3c, d ). Intriguingly, therewas an increase in total numbers of mono-nucleus cardiomyocytes and adecrease in bi-nuclei cardiomyocytes in miR-17-92-TG^(MHC) hearts (FIG.3e ). Consistent with the increase in the cell numbers, theproliferation of cardiomyocytes, marked by phosphorylated histone H3(pH3), was enhanced in miR-17-92-TG^(MHC) hearts (FIG. 3f, g ).Increased cell proliferation in miR-17-92-TG^(MHC) hearts was furtherconfirmed by 5-ethynyl-2′-deoxyuridine (EdU) incorporation andquantification (FIG. 3h, i ).

Example 3. miR-17-92 Induces Cardiomyocyte Proliferation in Adult Heartsand in Response to Injury

The above data indicate that overexpression of miR-17-92 was sufficientto induce cardiomyocyte proliferation in embryonic, neonatal and adulthearts. To further determine the function of miR-17-92 in theproliferation of postmitotic cardiomyocytes in adult hearts moredefinitely, an inducible system was utilized to overexpress miR-17-92 incardiomyocytes of four-month-old mice. The miR-17-92-KI mice were bredwith alpha-MHC-MerCreMer transgenic mice in which the Myh6 promoterdirects the expression of a tamoxifen-inducible Cre recombinase incardiomyocytes. miR-17-92 overexpression was induced in adultcardiomyocytes by activating tamoxifen-inducible Cre recombinase.Cardiac-specific overexpression of members of the miR-17-92 cluster wasconfirmed in the hearts of miR-17-92 transgenic mice (namedmiR-17-92-TG^(MerCreMer)) after tamoxifen administration (FIG. 4i ). Thehearts of miR-17-92-TG^(MerCreMer) mice were substantially larger thanthat of the littermate controls after miR-17-92 overexpression (FIG. 4a). Tissue sections revealed an increase in wall thickness and leftventricle dimension (FIG. 4a ). Whether overexpression of miR-17-92 inadult cardiomyocytes could induce cell proliferation was also examined.Using EdU incorporation assay, a marked increase in the EdUincorporation in the cardiomyocytes of six-month oldmiR-17-92-TG^(MerCreMer) hearts was found (FIG. 4b ). Cardiomyocytesfrom the hearts of miR-17-92-TG^(MerCreMer) and control mice wereisolated to determine the total numbers of cardiomyocytes, andoverexpression of miR-17-92 substantially increased total cardiomyocytenumber in adult hearts (FIG. 4c ). Quantitative measurement of the sizeof isolated adult cardiomyocytes showed that the size of cardiomyocyteswas reduced in the heart of miR-17-92-TG^(MerCreMer) mice (FIG. 4d ).

To test whether this cluster of miRNAs is involved in the regulation ofcardiomyocyte proliferation and cardiac repair in response to injury,myocardial infarction (MI) was induced by coronary artery occlusion(FIG. 4e ). MI results in massive cardiomyocyte death, cardiachypertrophy, fibrosis and cardiac remodeling. Overexpression ofmiR-17-92 in adult cardiomyocytes modestly protected the heart fromMI-induced injury (FIG. 4f ). Quantification confirmed the decrease inthe size of scar in the hearts of miR-17-92-TG^(MerCreMer) mice after MI(FIG. 4g ). Using EdU incorporation assay, a marked increase in the EdUincorporation in the cardiomyocytes of border zone ofmiR-17-92-TG^(MerCreMer) hearts was found (FIG. 4h ). Similarly, bothmiR-17-92 transgenic and control mice were treated with doxorubicin, acancer drug that can cause heart failure as side-effect, to inducestress. Overexpression of miR-17-92 modestly induced cardiomyocyteproliferation upon doxorubicin treatment.

Example 4. miR-17-92 is Sufficient to Induce Neonatal CardiomyocyteProliferation In Vitro

To test whether members of this cluster of miRNAs play a similar role incardiomyocyte proliferation in vitro, neonatal rat cardiomyocytes weretransfected with mimics or inhibitors of each member of the miR-17-92cluster and cardiomyocyte proliferation assayed^(17, 18). Cardiomyocytesisolated from postnatal day 1 (P1) hearts, in which cardiomyocytes arestill undergoing active proliferation, were used⁷. The followingmiR-17-92 mimic and inhibitor target sequences were used:

MIRIDIAN Mimic and Hairpin SEQ inhibitor target sequences ID NO:miR-17:  CAAAGUGCUUACAGUGCAGGUAG  6 miR-18a: UAAGGUGCAUCUAGUGCAGAUAG  8miR-19a: UGUGCAAAUCUAUGCAAAACUGA  1 miR-19b: UGUGCAAAUCCAUGCAAAACUGA  3miR-20a: UAAAGUGCUUAUAGUGCAGGUAG 10 miR-92a: UAUUGCACUUGUCCCGGCCUG 12

After being transfected with the miR-17-92 mimics or inhibitors, thecell culture was then incubated with EdU to label DNA synthesis and cellproliferation. Indeed, miR-17-92 mimics, especially miR-19a/b family,potently induced cardiomyocyte proliferation (FIG. 5a ). Conversely,inhibition of members of the miR-17-92 cluster, in particular miR-19a/b,substantially reduced cardiomyocyte proliferation, evidenced by thedecrease of EdU signal and the reduction of total cardiomyocyte numberswhen compared with controls (FIG. 5b ). Furthermore, postnatal day 4(P4) cardiomyocytes, in which cell proliferation starts to diminish,were treated with miR-17-92 mimics. The miR-17-92 mimics, miR-19a/b inparticular, significantly induced EdU incorporation. This observationwas further confirmed by quantitative analyses (FIG. 5h ). Theexpression of cyclin-dependent kinase 1 (CDK1), a highly conservedserine/threonine kinase involved in cell cycle progression¹⁹, wasexamined in miR-17-92 mimic treated cardiomyocytes. Consistent with theview that miR-17-92 induced cardiomyocyte proliferation, miR-17-92induced the expression of CDK1 in cardiomyocytes (FIG. 5c ).

Next, neonatal cardiomyocytes were isolated from miR-17-92-KI mice.Cultured cardiomyocytes were infected with ad-cTNT-Cre to induce theoverexpression of miR-17-92. Overexpression of miR-17-92 in mouseneonatal cardiomyocytes, but not the cells treated with the controlAd-lacZ, dramatically enhanced the incorporation of EdU, indicating anincrease in cardiomyocyte proliferation (FIG. 5d ).

Together, these data demonstrate that miR-17-92 mimics induce, whilemiR-17-92 inhibitors reduce cardiomyocyte proliferation in vitro and exvivo.

Example 5. miR-17-92 Represses PTEN to Induce CardiomyocyteProliferation

The expression of putative miR-17-92 targets that are known to play arole in cell proliferation was tested²⁰. It was reasoned that theexpression of these targets might be inversely correlated with theexpression of miR-17-92, which is decreased in the hearts ofmiR-17-92-TG mice and increased in the hearts of miR-17-92-KO mice.Indeed, the expression of several targets was elevated in the hearts ofmiR-17-92-KO mice (FIG. 5e ), and repressed in the hearts ofmiR-17-92-TG mice (FIG. 5f ). The experiments focused on PTEN, a tumorsuppressor and a member of family of protein tyrosine phosphatases²¹⁻²³,which was most dramatically altered in the hearts of miR-17-92transgenic and mutant mice (FIG. 5e, f ). PTEN has been supposed to be adirect target of miR-19a/b²⁴, the most potent member of the miR-17-92cluster to induce tumor growth²⁴ and to promote cardiomyocyteproliferation in the present study (FIG. 5a, b ). Deletion of PTEN leadsto axon regeneration in the central neural system, further highlightingthe role of PTEN in cell proliferation and regeneration²⁵. The nextexperiments asked whether PTEN could mediate the function of miR-19a/bin cardiomyocyte proliferation, and more specifically, whetheroverexpression of PTEN could suppress miR-19a/b-induced cardiomyocyteproliferation. PTEN was overexpressed in neonatal rat cardiomyocyteusing a modified RNA approach²⁶. Dose-dependent overexpression of PTENprotein was achieved in transfected cells (FIG. 5i ). Overexpression ofPTEN completely abolished miR-19a/b-induced cardiomyocyte proliferation(FIG. 5g ).

Example 6. miR17-92 Members Improved Cardiac Function in Post-MyocardialInfarction (MI) Hearts In Vivo

The following experiments were performed to demonstrate the ability ofmiR-17-92 members, specifically miR-19a/b, oligonucleotides to repairdiseased hearts after heart attack (myocardial infarction), or chronicheart failure, in an ischemic Injury Model-Myocardial infarction (MI)and a cardiac toxic model.

8 weeks old wild type C57BL/6 mice were randomly subjected tointra-cardiac injection of microRNA mimic miR-19a/19b or control mimics(10 ug per mouse), respectively, immediately after myocardium infarction(MI) surgery performed as described above.

Some of the mice were sacrificed at about 3 days after the surgery andmimic injection, and miR-19a expression levels were analyzed byreal-time Q-PCR using whole heart tissue. The results, shown in FIG. 7A,demonstrate increased expression of miR-19a after intra-cardiacinjection of miR-19a/19b mimics in post-MI hearts.

Echocardiography analyses of cardiac function were performed at 2 and 4weeks post-MI surgery from miR-19a/19b and control groups. N of eachgroup was indicated. The results, shown in shown in Table 3, demonstratethat left ventricular end diastolic posterior wall dimension (LVPW; d)and left ventricular end-systolic posterior wall dimension (LVPW; s)were increased. In contrast, both left ventricular end diastolicinternal dimension (LVID; d) and left ventricular end systolic internaldimension (LVID; s) were reduced in miR-19a/b injected heart, indicatingthat miR-19a/b prevents the progress of cardiac dilation. In addition,FIG. 7B shows that intra-cardiac injection of miR-19a/19b miR-19a/19bmimics improved cardiac function post MI, as indicated by increases inleft ventricular end diastolic posterior wall dimension and fractionalshortening.

TABLE 3 2-weeks-old 4-weeks-old Control miR-19a/19b Control miR-19a/19b(N = 5) (N = 10) (N = 3) (N = 2) IVS; d (mm) 0.478 ± 0.081 0.494 ± 0.0700.438 ± 0.068  0.671 ± 0.038* IVS; s (mm) 0.531 ± 0.096 0.620 ± 0.0760.501 ± 0.015  0.751 ± 0.076** LVID; d (mm) 4.915 ± 1.003 4.451 ± 0.6465.205 ± 0.422 4.252 ± 0.778 LVID; s (mm) 3.971 ± 1.210 3.150 ± 0.6854.150 ± 0.430 3.045 ± 0.854 LVPW; d (mm) 0.478 ± 0.052  0.580 ± 0.031**0.492 ± 0.031  0.590 ± 0.038* LVPW; s (mm) 0.671 ± 0.083 0.832 ± 0.1550.581 ± 0.031  0.724 ± 0.000** EF (%) 40.99 ± 15.49  56.65 ± 9.60**41.16 ± 6.137 55.82 ± 11.37 FS (%) 20.49 ± 8.80   29.80 ± 6.63** 20.33 ±3.451 29.04 ± 7.10  LV Mass (mg) 88.22 ± 24.90 84.61 ± 15.38 95.01 ±14.65 96.71 ± 30.26 LV Mass (Corrected, 70.58 ± 19.92 67.69 ± 12.3076.01 ± 11.72 77.37 ± 24.21 mg) LV Vol; d (uL) 119.07 ± 57.29  92.33 ±31.23 130.59 ± 23.71  82.93 ± 34.95 LV Vol; s (uL) 76.56 ± 53.64  41.82± 20.26* 77.19 ± 18.80 38.63 ± 24.87 Heart Rate (BMP) 634 ± 19  627 ±24  612 ± 46  657 ± 12* Table 3. 8 weeks old wild type C57BL/6 mice wererandomly subjected to intra-cardiac injection of microRNA mimicmiR-19a/19b and control, respectively, after myocardium infarction (MI)surgery. Echocardiography analyses of cardiac function were performed at2 and 4 weeks post-MI surgery from miR-19a/19b and control injectedgroups. N of each group was indicated. *P < 0.05; **P < 0.01 vs controlgroup. IVS; d: Interventricular septal thickness at diastole; IVS; sInterventricular septal thickness at systole; LVID; d: Left ventricularend diastolic internal dimension; LVID; s: Left ventricular end systolicinternal dimension; LVPW; d: Left ventricular end diastolic posteriorwall dimension; LVPW; s: Left ventricular end systolic posterior walldimension; EF: Ejection fraction; FS: Fractional shortening; LV Vol; d:Left ventricular end diastolic volume. LV Vol; s: Left ventricular endsystolic volume.

Mice were sacrificed at 2 weeks, or 4 weeks after surgery and histologyand immunohistology were examined. Fast green collagen staining was usedto mark the myocardium and Sirius red was used to visualize scar tissue.As shown in FIG. 7C, intra-cardiac injection of miR-19a/19b miR-19a/19bmimics reduced infarct size in post-MI hearts.

In addition, mice are sacrificed at 4 months, 6 months, 8 months, 9months, 10 months, and/or a year after surgery, and the expression ofcardiac marker genes, including ANF, BNP, cTNT, fetal and adult MHC, isexamined using quantitative RT-PCR and/or Western blots.

Example 7. miR17-92 Members Stimulate Cardiomyocyte Proliferation andCardiac Regeneration In Vivo in a Cardiac Toxic Model

The following experiments are performed to demonstrate the ability ofmiR-17-92 members, specifically miR-19a/b, oligonucleotides to repairdiseased hearts in a cardiac toxic model.

Cardiac Toxic Model

Doxorubicin (trade name, Adriamycin) is an anthracycline antibiotic usedin cancer chemotherapy. Doxorubicin treatment can produce a dosedependent dilated phenotype and heart failure over time after sufficientmyocardial injury and cell death. 2-4 months old male C57 mice will beused. After the mice receive subcutaneously buprenorphine (0.05 mg/kg)to provide analgesia, adult mice receive doxorubicin (2 intraperitoneal(i.p.) injections of 10 mg/kg at 3-day intervals, 20 mg/kg cumulativedose). Control animals are treated with only buprenorphine and i.p.saline. The mice are euthanized with carbon dioxide on days 1, 7, and 14after the last injection of doxorubicin.

All mice are given a single dose of 5 μg synthetic microRNA-19a/b(Dharmacon, Lafayette, Colo.) formulated with NLE according to themanufacturer's instructions by intra-myocardium injection. The NLE(MaxSuppressor in vivo RNALancerII) is purchased from BIOO Scientific,(Austin, Tex.). NLE consists of1,2-dioleoyl-sn-glycero-3-phosphocholine, squalene oil, polysorbate 20,and an antioxidant that—in complex with synthetic miRNAs—formsnanoparticles in the nanometer diameter range.

Cardiac function is analyzed by echocardiography measurement at 1, 2 and4 weeks after treatment. Mice are sacrificed about 4 weeks, 4 months, 6months, 8 months, 9 months, 10 months, and/or a year after finalinjection and histology, immunohistology will be examined. Theexpression of cardiac marker genes, including ANF, BNP, cTNT, fetal andadult MHC, is examined using quantitative RT-PCR and/or Western blots.

Example 8. AAV Mediated Delivery of Mir-19a/B

In some experiments, an AAV-based vector system, an especiallyattractive platform, is used for miR-19a/b delivery. There are severaladvantages of using AAV delivery system: 1) when delivered in viralvectors, miRNAs are continually transcribed, allowing sustained highlevel expression in target tissues. 2) The use of tissue-specificpromoters could restrict this expression to the heart (for example, theavailability of multiple AAV serotypes, especially AAV9, allows theexpression of miRNAs predominantly in myocardium of the heart). 3) AAVcarry substantially diminished risk of insertional mutagenesis sinceviral genomes persist primarily as episomes and the general safety ofAAV has been well documented, with clinical trials using this platformalready under way.

In these experiments, an AAV vector is generated to express precursorsof miR-19a/b (i.e., SEQ ID NO:2 or 4). AAV is administered at a dose of10¹² vg per mouse by tail vein injection (200 μl total volume) using a30 gauge ultra-fine insulin syringe. AAV-miR-19a/b is delivered in micewith myocardial infarction surgery and in aged mice with chronicallyheart failure (>18 months old).

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Other Embodiments

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

What is claimed is:
 1. A method of improving cardiac function in asubject, the method comprising: identifying and selecting a subject inneed of improving cardiac function; and administering to the selectedsubject a therapeutically effective amount of a microRNA (miR)-19a/19boligonucleotide.
 2. The method of claim 1, wherein, prior toadministering to the selected subject a therapeutically effective amountof a miR-19a/19b oligonucleotide, the subject is treated with acardiotoxic compound.
 3. The method of claim 1, wherein thetherapeutically effective amount is an amount sufficient to inducecardiomyocyte proliferation.
 4. The method of claim 3, wherein thecardiomyocyte proliferation is sufficient to increase cardiaccontractile force, or increase the thickness of the myocardium.
 5. Themethod of claim 1, wherein the miR-19a/b oligonucleotide is a singlestranded DNA or RNA that is at least 18, 19, or 20 nucleotides long, butless than 24 nucleotides long, and is at least 80% identical to SEQ IDNO:1 or 3, with 100% identity to nucleotides 1-8 of SEQ ID NO:1 or
 3. 6.The method of claim 5, wherein the miR-19a/b oligonucleotide comprisesat least one modification selected from the group consisting of:5′-phosphorylation; at least one 2′-fluoro ribose modification; and acholesterol moiety.
 7. The method of claim 5, wherein the miR-19a/boligonucleotide comprises SEQ ID NO:1 or
 3. 8. The method of claim 1,wherein the miR-19a/b oligonucleotide is a double stranded DNA or RNA,comprising: a first strand comprising a sequence that is at least 80%identical to 18, 19, or 20 consecutive nucleotides of SEQ ID NO:1 or 3,with 100% identity to nucleotides 1-8 of SEQ ID NO:1 or 3; a secondstrand comprising a sequence that is complementary to the first strand.9. The method of claim 8, wherein the double stranded DNA or RNAcomprises SEQ ID NO:2 or
 4. 10. The method of claim 8, wherein thedouble stranded DNA or RNA comprises at least one modification selectedfrom the group consisting of: 5′-phosphorylation; and 2′-O-methylribosyl substitution at position 2 in the first strand.
 11. The methodof claim 1, wherein the miR-19a/b oligonucleotide is administeredlocally to the heart of the subject.
 12. The method of claim 1, whereinthe miR-19a/b oligonucleotide is administered via a viral vector; ananoparticle or microparticle; or a gelfoam.
 13. The method of claim 1,wherein the subject is a post-neonatal, adolescent, or adult mammal. 14.The method of claim 13, wherein the subject is a human.
 15. The methodof claim 1, wherein the miR-19a/b oligonucleotide comprises at least 18,19, or 20 nucleotides with at least 80% identity to SEQ ID NO:1 or 3,including a region with 100% identity to nucleotides 1-8 of SEQ ID NO:1or
 3. 16. The method of claim 4, wherein the method includes detectingan improvement in cardiac function, an increase in cardiac contractileforce, or an increase in the thickness of the myocardium.
 17. The methodof claim 8, wherein the first stand and the second strand is linked by alinker therebetween.